Sql Server IF EXISTS THEN 1 ELSE 2

sql

best-practices

performance

sql-queries

byNikita Barsukov·Sep 3, 2024

For a fast track, use CASE statement along with EXISTS in T-SQL to return 1 if a row exists, else 2:

SELECT CASE WHEN EXISTS (SELECT 1 FROM yourTable WHERE yourCondition) THEN 1 ELSE 2 END

Swap yourTable with your actual table and yourCondition with the criteria defining the row's existence.

Efficient EXISTS Check

When performing the EXISTS check, for better performance, select a specific column or use TOP 1 in place of SELECT *. It reduces costs and runs faster:

IF EXISTS (SELECT TOP 1 1 FROM tblGLUserAccess WHERE GLUserName = 'xxxx') BEGIN SELECT 1 END ELSE BEGIN SELECT 2 END

Short and Sweet with IIF

For snappier, shorter conditional checks, IIF comes in handy. It simplifies syntax, making it more readable:

SELECT IIF(EXISTS(SELECT 1 FROM tblGLUserAccess WHERE GLUserName = 'xxxx'), 1, 2)

Analogous to IF..ELSE, but all wrapped up in a single line. As short as your morning coffee order!

Manage Complex Logic

Working with complex checks? Multiple use of results? Use a variable! It enhances readability and maintainability:

DECLARE @Result INT
IF EXISTS (SELECT 1 FROM tblGLUserAccess WHERE GLUserName = 'xxxx') SET @Result = 1 ELSE SET @Result = 2
SELECT @Result

It's a bit like lending someone your notes. With a variable, they're always at hand for future logic manipulation.

Syntax Police

Facing the "Incorrect syntax near '1'" error? That's because you didn't wrap the SELECT statements within BEGIN...END blocks using IF EXISTS. It's like trying to bake without preheating the oven! You'll need this:

IF EXISTS (SELECT 1 FROM tblGLUserAccess WHERE GLUserName = 'xxxx')
BEGIN
    SELECT 1
END
ELSE
BEGIN
    SELECT 2
END

Syntax errors, begone!

BEGIN..END with IF EXISTS

Your SQL script deserves a well-structured approach when dealing with IF EXISTS. Good habit? Encapsulate with BEGIN...END. A little like putting on seatbelts in a car. It indicates the start and end of the journey:

IF EXISTS (SELECT 1 FROM myTable WHERE condition)
BEGIN
    -- Buckle up! Let's kickstart the journey
    SELECT 1
    -- Keep the engine running. You might need more operations here
END
ELSE
BEGIN
    -- Hold on! The first route didn't work. Try another one.
    SELECT 2
    -- Additional actions on a detour come here
END