SQL: Is results order mapped to values in 'IN' expression?

Question

I have a list of record IDs for which I want to retrieve a single value from a table in SQL Server 2008.

My query is:

SELECT TestResult.FailureDetails FROM TestResult WHERE TestResult.ID IN (1,2,3,...)

The 'IN' expression contains hundreds of IDs. The ID column is the primary key of the table.

If my table is like:

ID    Value
1     A
2     B
3     C

Will I always get results ordered by order of appearance in the 'IN' expression? If not, I am considering doing:

SELECT TestResult.ID, TestResult.FailureDetails FROM TestResult WHERE TestResult.ID IN (1,2,3,...)

Answer 1

No, you will not always get results in order based on the IN.

Be explicit, and add an ORDER BY clause.

SELECT FailureDetails 
FROM TestResult 
WHERE ID IN (1,2,3,...) 
ORDER BY ID;