Can we use CASE statement in WHERE clause?

Can we use CASE statement in WHERE clause?

CASE can be used in any statement or clause that allows a valid expression. For example, you can use CASE in statements such as SELECT, UPDATE, DELETE and SET, and in clauses such as select_list, IN, WHERE, ORDER BY, and HAVING.

How do you use not exists in a case statement?

Case statement and if not exists

1. update STGtable.
2. Set processKey = CASE.
3. WHEN table1. DataValue is NULL or table1.
4. WHEN NOT EXISTS (SELECT 1 FROM DimProcess m where m. processCode = table1.
5. ELSE (select max(ProcessKey) from DimProcess m where m. processCode = table1.
6. END.
7. FROM STGtable INNER JOIN table1 ON ….

Why we Cannot use aggregate function in WHERE clause?

The reason you can’t use SUM() in the WHERE clause is the order of evaluation of clauses. FROM tells you where to read rows from. Right as rows are read from disk to memory, they are checked for the WHERE conditions. (Actually in many cases rows that fail the WHERE clause will not even be read from disk.

How do you use exists in a case statement?

Using EXISTS clause in the CASE statement to check the existence of a record. Using EXISTS clause in the WHERE clause to check the existence of a record. EXISTS clause having subquery joining multiple tables to check the record existence in multiple tables.

Which is the correct Behaviour of In & exists clause?

IN: Returns true if a specified value matches any value in a subquery or a list. Exists: Returns true if a subquery contains any rows. Join: Joins 2 resultsets on the joining column.

Can you USE CASE expression column in where clause?

Accordingly for the EXCEPT or INTERSECT cases. ORDER BY: rows are ordered. Therefore, you can’t use in WHERE clause, something that hasn’t been populated or calculated yet. See also this question: oracle-sql-clause-evaluation-order

How to use case when statement with exists in SQL?

SELECT * FROM dbo.CompanyMaster A LEFT JOIN @Areas B ON A.AreaId=B.AreaID WHERE A.AreaId= (CASE WHEN EXISTS (SELECT BusinessId FROM dbo.AreaSubscription WHERE AreaSubscription.BusinessId = CompanyMaster.BusinessId) THEN @AreaId ELSE B.AreaId END) ) Try putting SELECT top 1 [@Areas].AreaId FROM @Areas if it solves the issue..

How to check if column exists in SQL Server?

I’m using a SQL server statement embedded in some other C# code; and simply want to check if a column exists in my table. If the column ( ModifiedByUSer here) does exist then I want to return a 1 or a true; if it doesn’t then I want to return a 0 or a false (or something similar that can be interpreted in C#).

Why is column alias not used in where clause?

The (historic) reason behind this is the sequence of events in a SELECT query. WHERE and HAVING are resolved before column aliases are considered, while GROUP BY and ORDER BY happen later, after column aliases have been applied.