Why is my CASE expression returning an error?

Using the AdventureWorks file I typed the following query:

USE AdventureWorks2019

SELECT *
CASE 
    WHEN FirstName='Ken' THEN 1
ELSE 3
FROM Person.Person

But I keep getting the following error:

Msg 156, Level 15, State 1, Line 4
Incorrect syntax near the keyword ‘CASE’.

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Any ideas as to why this is?

>Solution :

You need a comma between the columns, and the CASE expression needs an "END" to terminate it, like so:

USE AdventureWorks2019

SELECT *,
    CASE 
        WHEN FirstName='Ken' THEN 1
        ELSE 3
    END as CaseColumn
FROM Person.Person

The as CaseColumn gives that column a specific name, which is optional but generally a good practice.