Case statement in where clause oracle performance. 7 WHEN 'B+' THEN 3. Description, Employee. Not procedural. Jul 11, 2013 · How to use case statement inside where clause in oracle? 1. i. Jan 14, 2016 · Oracle tries to filter the number of records to be scanned from table by going for the where clause first before select that is why your query fails. The CASE statement in SQL evaluates conditions and returns a result when the first condition equates to true: CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ELSE resultN END. A simple boolean or is equivalent. CASE with Conditional Aggregation. Thank you! Interested in getting your voice heard by members of the Developer Marketing team at Oracle? Check out this post for AppDev or this post for AI focus group Aug 30, 2021 · I am trying to write a "case" statement inside a "where clause" which has an "in" statement in the "then" part. 1. date, b. In the end, the subquery in the simple CASE expression was evaluated 4 times. Precisely, with CASE statement in WHERE clause, Oracle is not using index. The CASE expression goes through conditions and returns a value when the first condition is met (like an if-then-else statement). Hot Network Questions Nov 20, 2015 · Both solutions works well. COMPARE_TYPE = 'A' AND T1. The optimizer looks at the predicate, analyzes the available access paths, chooses the appropriate indexes and executes the query. And if the end date is empty, it should not filter on it. Here are some solutions to help you navigate these challenges: 1. id = b. . with bank_details as (Select 1 bank_id, 'First Bank' bank_name, 'N' auto_dep_flag from dual union all Select 2 bank_id, 'Deposit Bank' bank_name, 'Y' auto_dep_flag from dual union all Select 3 bank_id, 'Cash Transaction' bank_name, 'N' auto_dep_flag from dual ) select bank_name from A REGEXP_LIKE will do a case-insensitive regexp search. field value but a hardcoded value that is compared to perhaps a user selection or status (as examples) it might be a static value passed in via Apr 30, 2014 · As I commented below the CASE statement does indeed get around the issue. In almost all databases, it comes down to "the optimizer understands boolean expressions". Case your column and your string identically. with tmp as ( select 'Oracle' as field_name , 1 as data from dual union all select 'Oracle' as field_name , null as data from dual union all select NULL as field_name , null as data from dual union all select 'Test' as field_name , null as data from dual ) Select * from tmp Where 1 = case when field_name = 'Oracle' and data is null then 0 else 1 end Jun 8, 2015 · You can use a case: SELECT (columns list) FROM AGREEMENT A WHERE A. alter session set NLS_COMP=ANSI; alter session set NLS_SORT=BINARY_CI; Oct 15, 2012 · 2- is better to to Write 2 or more Queries each handling one option of the Case when value rather than writing a one Single Query having a case when statement. 7 WHEN 'F' THEN 0 ELSE Oct 20, 2013 · The CASE statement is evaluated in order, so if any "case" is true then every case after it is ignored. ) decode() is rather hard to follow. Aug 7, 2018 · CASE <expression> WHEN <comparison expression> THEN <return expression> … or. COL1=C1. NEXT_DATE IS NULL; can be written in another way I mean since It is using both AND and OR Operators on the same column . CASE WHEN <condition> THEN <return expression> your query is malformed. Create Procedure( aSRCHLOGI May 25, 2009 · I need help in a query using case statements in where clause. Feb 6, 2012 · Oracle SQL Case Statement in Where Clause. 3 WHEN 'B' THEN 3 WHEN 'B-' THEN 2. If it's not used often at all, it might be ok. index_id = p. The syntax for the CASE statement in a SQL database is: Oct 20, 2016 · It is not an assignment but a relational operator. What is Oracle Case Statement? Oracle Case Statement is similar to the IF-THEN-ELSE statement in PL/SQL but with the advantage of using it inside SQL without calling a procedure. 8 9 2) Case: 10 11 a) If the <search condition> of some <searched when clause> in 12 a <case specification> is true, then the value of the <case 13 It is NOT ALWAYS TRUE that there is no difference between join and where clause. But in Exadata , Decode is faster than CASE. ColumnName != '') OR (pEntityName IS NOT NULL AND e. This will lag your query. Thanks – ronan Jun 3, 2009 · For appeals, questions and feedback about Oracle Forums, please email oracle-forums-moderators_us@oracle. In addition: Don't use commas in the from clause. Apr 24, 2007 · Case construct with WHERE clause Hi Tom, I have a question and I don't know if this is possible or if i'm jsut doing something wrong because i get multiple errors like missing right paren, or missing keyword. Try writing the where clause this way: WHERE (T2. CASE expressions in WHERE clause (filter and join predicates) may result in incorrect join cardinality estimate and miscalculating the costs. May 5, 2012 · In my WHERE Clause IS the AND F. SQL/PLSQL Oracle query: CASE in WHERE statement. 7 WHEN 'D+' THEN 1. CustomerID Jan 3, 2014 · Oracle doesn't treat Boolean expressions like other expressions — it handles them as syntax rather than as a type — so CASE expressions can't evaluate to Booleans. However, how can we accomplish the same results differently by not using a CASE expression? The one I see recommended the most is using a UNION ALL operator. you can do it differently like this : Mar 15, 2021 · Is it possible to use a SELECT statement within case For ex, SELECT CASE WHEN A1. col1 matches B1. LEFT OUTER JOIN Table2 Table2 ON ( CASE WHEN Table1. Aug 7, 2013 · Try this. ID_DOC = D. Please suggest what may be done to improve its performance: Query: Sep 24, 2015 · The ordered_predicates hint is specified in the Oracle WHERE clause of a query and is used to specify the order in which Boolean predicates should be evaluated. select one, two, three from orders where orders. roleid AND rolename IN ( CASE WHEN (1 < 2) THEN ('Owner Role') WHEN (2 < 1) THEN ('Eval Owner Role') END); You can also write this without the case statement. 7 WHEN 'C+' THEN 2. When working with SQL CASE statements, there are a few common pitfalls you might encounter. column3 from Table a, (Select distinct b. rate, c. Here is what I have so far but I know I'm going down the wrong path; where. column2,a. Roughly, by using multiple WITH blocks (CTE's) I declare queries (I like to think them as ad-hoc views) to declare two distinct target set for both document types. Below is query I am trying to make work using a case statement Dec 30, 2008 · In my case the IDs come from a separate database. We have yet to look at the performance of CASE versus another method. index_id JOIN sys. Create Procedure( aSRCHLOGI Oct 9, 2013 · I believe you can use a case statement in a where clause, here is how I do it: Select ProductID OrderNo, OrderType, OrderLineNo From Order_Detail Where ProductID in ( Select Case when (@Varibale1 != '') then (Select ProductID from Product P Where . May 12, 2011 · The subquery in the IN clause does not depend on anything in the outer query. column1 like 'DEDUCTABLE%' Aug 5, 2022 · That means you want the result of the CASE expression to be a boolean. Thank you! Interested in getting your voice heard by members of the Developer Marketing team at Oracle? Check out this post for AppDev or this post for AI focus group Mar 24, 2015 · Both the statements will be having same performance as SQL Server is smart enough to parse both the same statements into a similar plan. Dec 4, 2013 · For appeals, questions and feedback about Oracle Forums, please email oracle-forums-moderators_us@oracle. The result of the case statement is either 1 or 0. hobt_id THEN 1 WHEN a. You can either put your query in a subselect: SELECT gpaScore FROM (SELECT ( CASE grade WHEN 'A+' THEN 4 WHEN 'A' THEN 4 WHEN 'A-' THEN 3. However, my CASE expression needs to check if a field IS NULL. The problem with the case (as you have written it) is that Oracle does not treat the value from a logical expression as a valid value. Oracle doesn't "know" that all the employees returned be the query will be in the Sales department, so it can't use that information to reduce the set of data to work with before performing the CONNECT BY. I would continue to work with your vendor on indexing strategies if possible. bid where a. Always use proper, explicit, standard, readable JOIN syntax. partitions p ON i. So, when possible, rewrite lengthy IF-THEN-ELSIF statements as CASE statements. NEXT_DATE = V_NEXT_BUSINESS_DATE OR F. However, as not all the input fields are mandatory from the front end, I have to use CASE statement in WHERE clause. Compare and contrast the CASE WHEN statement with the IF statement in SQL. Example: Select Acc , Case when Calculation_type = 'M' then Min_value when Calculation_type = 'E' then Ending_value Else Average_BLC END From Table alternative Dec 14, 2020 · Using DECODE() function containing CASE. See this FAQ for details. Mar 22, 2011 · There are 3 main ways to perform a case-insensitive search in Oracle without using full-text indexes. D_OrganizationID > 2 THEN OrganizationDesc. Table1 Table1. ELSE 'Other Traffic' END AS ORGANIZATION, Complex CASE expressions can affect query performance in multiple ways. May 22, 2021 · There is a major, major difference between using a CASE expression and boolean expressions in the WHERE clause. The SQL CASE statement specifies a conditional expression to perform different actions depending on the input expression value. CASE allows you to perform IF-THEN-ELSE logic in your SQL statements, similar to DECODE. Mar 9, 2006 · Here is an example of the query: SELECT. These statements allow you to apply conditional logic directly within your SQL queries, enabling powerful data transformations and insights. 2. This would speed the 'report' up -- perhaps to well under 1 second. SOME_TYPE LIKE 'NOTHING%') OR (T2. Forget performance for a minute. Tried a whole host of methods using STRAGG and in-list functions but kept running into limitations Thanks for showing how I can do dynamic where clauses without using pl/sql. As a WHERE clause already is a boolean expression, you don't need CASE expressions there, anyway. select a. 1) LEFT JOIN the JOBS table and then use your CASE statement. orderid = CASE WHEN @orderid > 0 then @orderid ELSE orders. Case statements defined on variables. I have a table with the below data, SELECT DEPT_NO, DEPT_NAME FROM SORTNG_LOGIC; DEPT_NO DEPT_NAME Jun 9, 2011 · My query has been modified to use a CASE statement in the WHERE clause to consider data from certain columns based on a parameter value. Aug 20, 2018 · If I remove the CASE statement from WHERE clause and pass something like where col1=p_field1) the index is used and the query performance is very good. Thanks! – Oct 30, 2017 · Here is the query that you can use. This scenario can almost always be rewritten to improve performance. Theoretically, the optimizer can take the version without the case and apply an optimization that transforms the subquery in your filter into a join; when the case statement is added this optimization is no longer possible and the subquery is executed for every row. I don't want to write a Dynamic SQL. The Decode operation is done at storage Server level where the data is present BUT CASE is done at DB Instance level which receives data from DB storage Level. CASE expressions require that they be evaluated in the order that they are defined. 3 WHEN 'D' THEN 1 WHEN 'D-' THEN 0. So, once a condition is true, it will stop reading and return the result. employeeid = employeerole. case in where clause - Toad SQL. The question was the following: Assuming a variable @var that is an integer and has a value of 0 (zero). CREATE TABLE performance_test AS ( SELECT * FROM dba_objects ); SELECT * FROM performance_test WHERE object_name IN ('DBMS_STANDARD', 'DBMS_REGISTRY', 'DBMS_LOB' ); Even though the query uses IN, the Execution Plan says that it uses OR: May 17, 2023 · Alternatives to CASE. 2) Keep my CASE statement with your SELECT 1 FROM JOBS J WHERE J. So it’s about applying a mechanism that lets SQL Server filter as opposed to a straight scan. May 5, 2015 · The case statement is an expression that returns a single value. Does anybody have any idea what the correct syntax should be like?. "The CASE expression cannot be used to control the flow of execution of Transact-SQL statements, statement blocks, user-defined functions, and stored procedures. EmployeeName, Employee. Also, calling EXPLAIN PLAN on any query you're going to use in production is a must. So, it does not matter if you use WHERE or HAVING in your query. 0. WHERE ( :APP_USER = 'xxx. Always use proper, explicit join syntax. Select CASE SQL To add to Alex's answer: The CASE expression has two forms, the "simple" CASE expression and the "searched" CASE expression. Example: Count of employees in each performance category Oct 17, 2024 · The PL/SQL CASE statement is a powerful conditional control structure in Oracle databases that allows you to execute different blocks of code based on specified conditions. Oracle with CASE Statement Jul 14, 2018 · Following oracle query complies and works fine: SELECT Employee. But, ideally you should use WHERE clause syntactically. As you're checking whether the result of the case statement is the same as the ELSE clause then the statement is the same as the opposite of all other conditions. Just use AND, OR, and the appropriate parentheses. At least for built-in functions, Oracle should be able to figure out that it could evaluate it only once. status. ID_DOC withount joining the JOBS table. May 15, 2014 · For appeals, questions and feedback about Oracle Forums, please email oracle-forums-moderators_us@oracle. SOME_TYPE LIKE 'NOTHING%' ELSE T1. BusinessId = CompanyMaster. D_OrganizationID = 0 THEN 'Unknown Consumer'. roleid = roledef. UserID, U. (For user-defined functions, see below). SOME_TYPE NOT LIKE 'NOTHING%' END I know that my WHERE is clause is not correct. Jun 23, 2020 · A short time ago we were introduced the incredibly useful and versatile Case Statement. I've tried this: Jun 2, 2023 · You can’t reference the CASE statement like the example you gave, because it’s referring to a column alias, which can’t be done inside a WHERE clause. DECLARE @AreaId INT = 2 DECLARE @Areas Table(AreaId int) INSERT INTO @Areas SELECT AreaId FROM AreaMaster WHERE CityZoneId IN (SELECT CityZoneId FROM AreaMaster WHERE AreaId = @AreaID) IF EXISTS (SELECT BusinessId FROM dbo. Aug 1, 2017 · I have a WHERE clause that I want to use a CASE expression in. However, you can achive this in your WHERE clause without using a CASE statement: WHERE (desc1 = 'desc1' AND status_code IN (240,242)) OR (desc1 = 'desc2' AND status_code IN (240,245)) Feb 12, 2014 · Is it possible to use between operator within a CASE statement within a WHERE Clause ? For example in the code below, the condition should be pydate between (sysdate-12) and (sysdate-2) if its a mo Sep 17, 2021 · I have a select statement like below select * from employees where emp_id <= v_emp_id; I want this emp_id to be <= v_emp_id if country is not USA. Aug 4, 2020 · I am new to PL/SQL and trying to write conditional statement in join condition like below. Jan 12, 2015 · Complex Case Statement in Oracle SQL. Jul 7, 2024 · In contrast, the CASE WHEN statement is used across multiple SQL dialects, including PostgreSQL, MySQL, Oracle, and SQL Server, in SELECT, UPDATE, and DELETE statements to handle multiple conditions. I get 10k IDs from DB-A and need to get data from DB-B for each one. xxx' AND tmp. If CASE is only being used to transform the final output of a query, and it's actually possible to replace the same functionality with an if or select case in ASP, then it probably means that the database query/procedure is trying to do things that Nov 2, 2023 · Here, the SQL CASE statement checks for NULL values in PerformanceRating and marks them as 'Pending Evaluation'. In the absence of ordered_predicates, Oracle uses the following steps to evaluate the order of SQL predicates: Jul 5, 2021 · In PL-SQL using nvl will be easier that is true. type IN (2) AND a. However, dynamic SQL seems like overkill in this case. the WHERE clause? For example-- Condition in JOIN SELECT * FROM dbo. There, it may be utilized to alter the data fetched by a query based on a condition. Feb 9, 2024 · A CASE expression returns a scalar value and not an expression (or list of expressions). Jul 11, 2016 · I look for a working example where I can use mutliple when case statment wihch check to verify if a specific text is contained: e. Create Procedure( aSRCHLOGI This is working Oracle example but it should work in MySQL too. Introduction to SQL CASE Statement. Thank you! Interested in getting your voice heard by members of the Developer Marketing team at Oracle? Check out this post for AppDev or this post for AI focus group Aug 20, 2008 · I had played around with using the CASE statement in the where clause to sql more dynamic but had also run into the same problem with needing multiple values returned for the in. If you want to use case, then you need to return a value and do a comparison: (CASE order_date > sysdate and fee_rate_type in ('REGULAR', 'BONUS') then 1 order_date <= sysdate and FEE_RATE_TYPE in ('REGULAR') then 1 END) = 1 Sep 29, 2010 · I want to use Case statement in where clause for Example Select a. Table1. Below is how you would write a statement to avoid using Mar 27, 2012 · Im trying to avoid unioning multiple select statements by utilizing a CASE inside a WHERE clause. – Jeffrey Kemp Sep 3, 2018 · An even better solution is to add to a Summary Table every month. col1 then select from A1 and B1 and if not select from A1 and C1 Thanks Dec 2, 2011 · Depending on your use case, instead of using a case statement, you can use the union of multiple select statements, one for each condition. In what scenarios would you prefer using a CASE WHEN statement over using a JOIN clause? Apr 21, 2012 · A CASE expression returns a value from the THEN portion of the clause. column1 like 'DEDUCTABLE%' May 26, 2016 · I believe that a CASE statement can only return one value (corresponding to one column in the result set). column2) Thanks for your help Mastering SQL CASE WHEN statements is critical for anyone working with relational databases, whether using SQL Server, MySQL, PostgreSQL, or another database management system. On the other hand, what makes a difference is data type used in the boolean expression. "1", however doing so does not accomplish my goal. AreaSubscription WHERE AreaSubscription. field = @var or @var = 0 Jun 26, 2023 · This SQL tutorial will guide you on conditionally filtering using the WHERE clause using a SQL CASE statement. When the parameter is defined as 'New Items' it should utilize one code and for 'Updated Items' another condition. column1 is not null then a. ColumnName = pEntityName); May 17, 2013 · SELECT STATEMENT INLIST ITERATOR INDEX RANGE SCAN This seems to imply that when you have an IN list and are using this with a PK column, Oracle keeps the list internally as an "INLIST" because it is more efficient to process this, rather than converting it to ORs as in the case of an un-indexed table. Another win for the MSSQL case (no pun intended!!) Sep 30, 2016 · I'm interesting that how can I use if-then-else statement or any control structure in where clause in Oracle. I was using Oracle 10gR2 above. Currently doing a massive IN (1,2,. Another way to use the Case Statement is within the WHERE clause. I optimize the long running queries all the time and sometimes the queries using where clause perform better than those using join by a factor of up to 70x. Jul 2, 2014 · @ErwinSmout - I can't believe I never followed up on your comment. CASE statements can be used in different SQL clauses like SELECT, UPDATE, INSERT, WHERE, ORDER BY, and more depending on the Oracle SQL CASE statement gives you the flexibility to use sql IF ELSE logic in a SELECT, WHERE and JOIN clause. * from . name = 'xxx' select * from #t where rate>0 Mar 9, 2011 · For appeals, questions and feedback about Oracle Forums, please email oracle-forums-moderators_us@oracle. Like procedure samp (pId number, pValue varchar, details out T_cursor) is begin Open details for Select id, No,Name from tbl1 where. Customers AS CUS INNER JOIN dbo. You are missing smth - see IN after END Replace 'IN' with '=' sign for a single value. COMPARE_TYPE <> 'A' AND T1. CASE Jun 29, 2011 · Is it possible to use a SELECT statement within case For ex, SELECT CASE WHEN A1. EmployeeId, Employee. Another option is dynamic SQL, where you actually create a string with the SQL statement and then execute it. customer_id IS NULL; and when pcustomer_id IS NOT NULL then c. The Feb 26, 2016 · The problem is that Oracle evaluates the SELECT after the WHERE clause. TableName e WHERE (pEntityName IS NULL AND e. column1 = b. Thank you! Interested in getting your voice heard by members of the Developer Marketing team at Oracle? Check out this post for AppDev or this post for AI focus group Oct 16, 2008 · The problem with this is that when the SQL engine goes to evaluate the expression, it checks the FROM portion to pull the proper tables, and then the WHERE portion to provide some base criteria, so it cannot properly evaluate a dynamic condition on which column to check against. allocation_units a ON CASE WHEN a. If you want to find all the exam results with A or B grades, you can place the select above in a subquery. Thank you! Interested in getting your voice heard by members of the Developer Marketing team at Oracle? Check out this post for AppDev or this post for AI focus group Aug 4, 2020 · I am new to PL/SQL and trying to write conditional statement in join condition like below. 4 Common Pitfalls and Solutions With SQL CASE Statements. Case expression in where clause in Oracle. Apr 21, 2020 · The ranges set out in the case statement all differ, with no discernible pattern between them. Mar 5, 2023 · Guffa has the right answer, but the way you'd do this using the CASE trick (which does occasionally come in handy) is this:--If order ID is greater than 0, use it for selection --otherwise return all of the orders. I do the same for the business_unit column with a second CASE statement. (This does not affect performance, however. id = c. I want to use as: when pcustomer_id IS NULL then WHERE c. Both perform good. Unfortunately, I still need to use this in Oracle. type IN (1, 3) AND a. CASE expressions found in SELECT list are CPU-intensive operations. Different versions of Oracle have different options for plan stability-- there are stored outlines Aug 20, 2019 · The option type = '1' is common in both cases so you can leave it out of the CASE statement (also because it would be syntactically wrong to try to return 2 values from the CASE statement): where type = '1' and status = case when carName = :P_PARAMETER then 'N' else 'Y' end Apr 29, 2024 · 1 1) Case: 2 3 a) If a <result> specifies NULL, then its value is the null 4 value. employeeid AND employeerole. Always remember that distinct removes duplicates so May 16, 2017 · Here's another attempt without using a CASE STATEMENT but returns no result: SELECT e. There are a number of examples using the CASE WHEN construct in SQL, such as the SELECT columns or in ORDER BY clauses, but we tend to forget CASE can be used wherever an expression is expected. Jan 11, 2016 · I am facing difficulty in understanding oracle(12c) sql order by clause with case statement. column1,b. Jan 19, 2012 · Is it possible in Oracle to put conditional IF statements in the WHERE clause? I want to filter all rows with an end date before today. Oracle SQL doesn't support a boolean data type, though, so the expression is invalid. ACCOUNT = 545 AND A. OrganizationLevelLabel AS ORG_LEVEL, CASE WHEN op. I hope this would be allowed in Oracle PL/SQL) select . If I replace them with case will it work faster? For example; select case sum(nvl(birikim,0)) when null then 0 else sum(nvl(birikim,0) end Next, let’s go over some common pitfalls when working with SQL CASE statements so that you can improve your code quality. My goal when I found this question was to select multiple columns conditionally. Nov 19, 2011 · There's a more fundamental question that's not being asked here: What are these CASE statements actually doing?. If no conditions are true, it returns the value in the ELSE clause. I'm here looking for more performant alternatives :) – Mar 27, 2012 · Im trying to avoid unioning multiple select statements by utilizing a CASE inside a WHERE clause. I have multiple case statements running on the same column. COL1 FROM A1,C1 WHERE A1. If it was that simple and straightforward, life would be all rainbows and unicorns. com. COL1 FROM A1, B1 WHERE A1. The CASE statement in Oracle isn't a function, so I haven't labelled it as one. for example. BusinessId) BEGIN SELECT * FROM dbo. type, a. AND (CASE E WHEN spriden_ntyp_code = 'CHSN' then spriden_ntyp_code = 'CHSN' WHEN spriden_ntyp_code <> 'CHSN' then spriden_change_ind IS NULL Feb 15, 2022 · i tried Case in With clause but still failed, please help. I could of course write an IF block with 7 ELSE statements essentially writing the same select statement 7 times, but I'm guessing the above can't be too far off. Jan 29, 2014 · According to Oracle's documentation linked to in the answer, "To write a query that performs an outer join of tables A and B and returns all rows from A (a left outer join), use the LEFT [OUTER] JOIN syntax in the FROM clause, or apply the outer join operator (+) to all columns of B in the join condition in the WHERE clause. aid c inner join b. COL1, C1. NAME, D. column2 is not null then a. Apr 22, 2019 · I can't tell for sure without seeing an execution plan but the branch in your filter is likely the cause of the performance problems. CustomerID = ORD. 13. Having issue with the following I know CASE statements in WHEREs are allowed just can't get it working for this one. if :P21_TYPEID value is 1 then in where clause it should be PARENTID_1 in (10,11) otherwise PARENTID_1 = :P21_TYPEID. BETWEEN is unnecessary assuming that datet is not in the future. container_id = p. But when it comes to query (in select statement) will using nvl make it slower? I have a package that have loads of select statement with NVl. GRP_ID ELSE ? END And Decode works in a similar fashion, although I think it's less readable. This comprehensive guide will explore the syntax, use cases, and practical Dec 3, 2014 · You just need to make both comparisons in the same case statement: and dep_dt = case when to_char( SysDate, 'D' ) <> '2' and dep_dt <= SysDate then dep_dt else SysDate end Jun 16, 2011 · Here's another way of writing it which may address concerns about accessing the second table more times than necessary. Technical questions should be asked in the appropriate category. COL1 END FROM A1,B1,C1; That is if A1. If you got yourself down to a single sharable SQL statement, then in addition to avoiding the cost of constantly re-parsing the statement, you'd have a number of options for forcing a particular plan that don't involve modifying the SQL statement. Here, we explore the syntax, types, and practical use cases of the PL/SQL CASE statement to make better decisions and improve your ability to use conditional logic in Oracle Feb 18, 2014 · Nice. Ultimately what method you choose is dependent on your individual circumstances; the main thing to remember is that to improve performance you must index correctly for case-insensitive searching. Instead, use AND and OR:. COL1 THEN SELECT A1. SELECT count(*) FROM userTable WHERE ( CASE WHEN mac IS NULL THEN mac IS NULL ELSE mac = '000fe95erd32' END ) your clause is not well good. " Reference Aug 19, 2010 · For appeals, questions and feedback about Oracle Forums, please email oracle-forums-moderators_us@oracle. ColumnName FROM Schema. You can safely move it into FROM clause; a sane query plan builder would do it automatically. This modified query is doing a full table scan and running endlessly. column1 when b. COL1, B1. DEPARTMENT, U. 5 6 b) If a <result> specifies a <value expression>, then its value 7 is the value of that <value expression>. Nice work. FirstName = 'John' -- Condition in WHERE SELECT * FROM dbo. Same execution time. 438932 Apr 14 2008 — edited Apr 14 2008. Orders AS ORD ON CUS. Based on your first procedure example and the time difference between the C#-generated version and the proc, I'm guessing the WHERE clause in the proc version is killing any chance of optimization - probably the C# version has a much more targeted WHERE clause. WHEN expression in it for the case flag_a='B' might be an alternative way to get the desired results such as SELECT no, SUM(qty) AS qty FROM ppp WHERE DECODE(flag_a,'P',0,'C',1,'B', CASE WHEN flag_b IN (0,1) THEN flag_b END)=flag_b GROUP BY no Oct 24, 2018 · Your lead is wrong. In a "simple" CASE expression you compare one expression to one or more values; that doesn't work with NULL, as we know from the first week of SQL classes. If country is USA, then I want emp_id to Jun 18, 2013 · As for your question "does the entire statement need to be dynamic sql", the answer is yes. Do it and see what the DBMS thinks of the plan for this query. If there is no ELSE part and no conditions are true, it returns NULL. So, in the first usage, I check the value of status_flag, returning 'A', 'T' or null depending on what it's value is, and compare that to t. If the @UserRole variable value = 'Analyst', then the SupervisorApprovedBy column value must be NULL. – Oct 19, 2017 · Lose the "distinct". g. column1,a. COL1 ELSE SELECT A1. column2 from tableb) b where (Case when b. Also, something needs to be done about the terribly long landing_page. ", I didn't find a significant difference between three styles of conditionals. value into #t from a inner join b on a. Jul 12, 2012 · But it should alleviate the slowness in this case. D_OrganizationID = 2 THEN 'Undefined Consumer'. select * from Users where Regexp_Like (User_Name, 'karl|anders|leif','i') This will be executed as a full table scan - just as the LIKE or solution, so the performance will be really bad if the table is not small. Any help would be great in knowing if this type of statement is possible. Jun 21, 2018 · E. In fact there is no such thing as a case statement in SQL Server, it is a case expression. COMPARE_TYPE WHEN 'A' THEN T1. Oct 1, 2024 · SQL CASE Statement Basics. employee Aug 23, 2024 · 12. WHEN op. What is the best scenario?a) SELECT () WHERE @var = 0 or May 28, 2017 · Although the documentation says "The CASE statement is more readable and more efficient. Apr 14, 2008 · Oracle has updated its online CASE statement in where clause. ) Else (Select ProductID from Product) End as ProductID ) FROM T1, T2 WHERE CASE T2. Dec 7, 2023 · How to use CASE in the WHERE clause. Then filter it in the outer query. What is the best scenario? a) SELECT () WHERE @var = 0 or table. Basically, the following code is what I want, but it's not the Oracle correct syntax. emp WHERE (CASE WHEN job = 'MANAGER' THEN '1' WHEN job = 'CLERK' THEN '2' ELSE '0' END) IN (1, 2) Aug 13, 2021 · This tutorial will explain how to use Oracle Case Statement expression with basic syntax and many examples for better understanding. I want to use the CASE construct after a WHERE clause to build an expression. If you want to use the CASE statement in the WHERE clause, you’ll need to copy and paste the same CASE statement, instead of use the “continent” name. I tried to put it in case statement but it didn't work. SELECT empno, ename, job FROM scott. Actually I am passing a value in a procedure according to the value i have to select fields in where clause. SUM(NVL()) is not needed, because NULL values are ignored. In that blog, we employed the Case Statement as most DBAs and developers do, in the SELECT clause. STATUS, Oct 2, 2018 · (1) you can't use a case statement anywhere in a sql query; (2) you can use a case expression anywhere in a sql query where an expression is allowed, including the select and where clauses. But having erratic performance. Which access is faster depend upon the selectivity of the inner query and the clustering of the index on TABLE1 (are the rows with similar value of col2 in TABLE1 next to each other or randomly spread?). SQL case query with multiple statement. Apr 6, 2021 · We also saw 4 CASE WHEN expressions in the Compute Scalar operator. Getting an actual filtering mechanism in place, performance shoots through the roof. How can I do it? Jul 4, 2009 · Query A says start with managers in the Sales department and then get all their employees. Nested CASE statements in SQL. Case statement in where. Some databases do, but not Oracle. column2 = b. To avoid such performance problem as multiple CASE statement in SQL, we need to rewrite the query. IsFrozen FROM employee, employeerole, roledef WHERE employee. ol. Or you can slap the case expression directly in the where clause, like so: May 29, 2012 · The order of evaluation of the where clause in a SQL statment is purposely "undefined". Note: same CASE statement is used in PL/SQL blocks. ,1000) statement. Hi all, Oct 18, 2009 · SELECT col1 as a, CASE WHEN a = 'test' THEN 'yes' END as value FROM table; I am trying to alias the column because actually my CASE statement would be generated programmatically, and I want the column that the case statement uses to be specified in the SQL instead of having to pass another parameter to the program. In any case, performance wise Mar 14, 2013 · The CASE statement evaluates multiple conditions to produce a single value. CASE in WHERE statement. select col1,col2, case when col3='E01089001' then 1 else 2 end, case when col3='E01089001' then 3 else 4 end end from Table1, dual where col1='A0529'; Apr 12, 2023 · You can define case statements in the column formula of reports or in the Oracle Analytics repository (RPD) file. Jun 8, 2016 · My query has a CASE statement within the WHERE clause that takes a parameter, and then executing a condition based on the value entered. compute_zone = case when :P14_zone is NOT NULL Mar 31, 2020 · I never use case statements is a where clause, I have this case statement. Here is a case where an index is being used (and the function is not evaluated for every row): Jun 19, 2010 · I tried it with Oracle, and it was exactly the same. Thanks for accepting this as the answer but Tony Andrews solution is a lot more straightforward and, in my view, the better answer. In your case, I think the clearest code is if you just rewrite it a bit: Jun 23, 2009 · Use ALTER SESSION statements to set comparison to case-insensitive: alter session set NLS_COMP=LINGUISTIC; alter session set NLS_SORT=BINARY_CI; If you're still using version 10gR2, use the below statements. Sep 21, 2015 · I'm trying create report filters using substitution variables in case statement in a where clause. You could use it thusly: SELECT * FROM sys. I've never had the need to use a CASE statement in a WHERE clause in this way before Oct 13, 2010 · Hello gurus, Can we use case statements in where clause ?? Any example will be great! And also i would like to know, besides CASE and DECODE statements, Is there any way we can use IF ELSE statemen Jan 5, 2021 · Never use commas in the FROM clause. col1 then select from A1 and B1 and if not select from A1 and C1 Thanks Feb 11, 2011 · In that case Oracle will read the rows from TABLE2 and for each (unique) row, perform an index access on TABLE1. Jul 7, 2010 · From performance perspective, In Oracle decode and CASE does not make any difference. You select only the records where the case statement results in a 1. Apr 2, 2020 · Case construct with WHERE clause Hi Tom, I have a question and I don't know if this is possible or if i'm jsut doing something wrong because i get multiple errors like missing right paren, or missing keyword. The SQL CASE statement within aggregation functions allows conditionally aggregating data based on certain criteria. We can (and in fact do) change the order of evaluation whenever we feel like it. While the CASE statement works in a way that is similar to a WHERE clause, it’s not a WHERE clause and therefore, scans. field = @var b) SELECT () WHERE table. It's specified in terms of the overall logic and, so long as it still logically computes the result it's asked to, the evaluation order should not matter. I'm not really sure how to write this. customer_id = pcustomer_id. 3 WHEN 'C' THEN 2 WHEN 'C-' THEN 1. I've read that when using a CASE statement within a WHERE clause you have to surround the statement with parenthesis and assign it to a numeric value, e. The difference here is that SQL is a declarative language. Use table aliases that are abbreviations for the table names. Moreover, your query would have never returned rows with department - "Accounts or Unknown" because of the filter Department="SALES" As shown in the output, the statement returned the number of products for each product that appears in the order_items table. Borrowing your example var l varchar2(4); exec :l := '551F'; with rws as ( select '551C' assembly_line from dual union all select '551S' assembly_line from dual union all select '551F' assembly_line from dual union all select '1234' assembly_line from dual ) select * from rws where case when :l Apr 7, 2016 · WHERE clause in query - does order really matter? Dear Tom,Yesterday we had a discussion at lunch regarding the performance impact of how the WHERE clause is constructed. And don’t forget to take the quiz . Oct 20, 2016 · You can also go the other way and push both conditionals into the where part of the case statement. The HAVING clause restricted the products to those that were CPU (category id 1) with the number of products greater than 5 and Video Card (category id 2) with the number of products greater than 2. All too often, I see the distinct clause used as a Band Aid for poor data structures, at the cost of [dire] performance. COL1=B1. CustomerID AND CUS. indexes i JOIN sys. SELECT ID, NAME, (SELECT (Case when Contains(Des Is there any difference (performance, best-practice, etc) between putting a condition in the JOIN clause vs. Answer: Unlike the IF statement, CASE WHEN is SQL’s standard conditional construct and provides a more readable and flexible solution for handling multiple conditions. Sep 12, 2005 · How and when a "CASE" is executed with in a statement? currently when using a CASE i have serious performance issues even though the consistent gets are low? Thanks, March 18, 2003 - 4:43 pm UTC Feb 21, 2019 · I’m commonly asked whether whether I can have a CASE Statement in the WHERE Clause. The case logic can be used within an INDEXCOL function, enabling Oracle Analytics to simplify the execution of the case Dec 2, 2020 · In the case of using Dynamic SQL there are times when a CASE Statement MUST be used due to the fact that there could be data that is being compared against in the WHERE clause that is NOT a column. partition_id THEN 1 ELSE 0 END = 1 May 3, 2016 · The CASE Statement. Therefore, no need for the over-complicated UNION hack (which incidently gives the same cost as the CASE). Technical questions should be asked in the appropriate category. CompanyMaster WHERE AreaId IN (@AreaId) END ELSE BEGIN Jul 19, 2011 · It is a perfect scenario for using CASE statement in WHERE clause, and here is the complete query in Oracle PL/SQL: SELECT U. The question was the following:Assuming a variable @var that is an integer and has a value of 0 (zero). GRP_ID = CASE ? WHEN 0 THEN A. How to Avoid Multiple Evaluations of a Subquery in a Simple CASE Expression. SOME_TYPE NOT LIKE 'NOTHING%') Share Apr 7, 2016 · Yesterday we had a discussion at lunch regarding the performance impact of how the WHERE clause is constructed. end; In where clause i want Jan 17, 2020 · Hello Tom Is it possible to change the where condition (using case statement) based on certain variable? For example var T varchar2(1) exec :T := 'E'; var E number; exec :E := 7788; var N varchar2(20) exec :N := 'MILLER'; select empno, ename from emp where -- how to use case statement to vary the condition based on :T -- if :T = 'E' then the condition should be where empno = :E -- and if :T Jul 14, 2009 · I do not think this is generally the case, as it would prevent an index from being used. That's the one we'll compare against. orderid END Apr 2, 2020 · Case construct with WHERE clause Hi Tom, I have a question and I don't know if this is possible or if i'm jsut doing something wrong because i get multiple errors like missing right paren, or missing keyword. Jan 4, 2012 · I posted the following question yesterday: Multiple 'in' statements in a where clause that need to match against each other In this there was some discussion about a feature in Oracle which doesn't exist in Microsoft SQL, the specific line of code being: Jul 7, 2017 · And this is where the WITH clause comes in.