Comparison in SQL Server CASE clause

Question

How would I go about the following query?

SELECT
CASE LEN(field1)
WHEN > 15    --Error: Incorrect syntax near '>'.
THEN SUBSTRING(field1, 1, 15)
ELSE field1
END
AS 'My Field'
FROM MyTbl

Can you not do comparisons like this in a CASE clause?

Answer 1

SELECT
CASE 
WHEN LEN(field1) > 15
THEN SUBSTRING(field1, 1, 15)
ELSE field1
END
AS 'My Field'
FROM MyTbl

When you write it the way you had it, think of it like a switch statement, where you're making implicit equality comparisons. If you need more complex logic you need to write the CASE this way.