Question

I encountered sql queries like 'SELECT 1 FROM TABLE_NAME' or 'SELECT 2 FROM TABLE_NAME' while debugging a program. I am curious as to what the numbers in the queries do and what result set does it return.

Thanks

Answer 1

It will return a single column with the number as value, with n rows, n being the number of rows returned from the select.

This is usefull in cases such as

SELECT *
FROM YourTable yt
WHERE EXISTS(
    SELECT 1
    FROM SomeOtherTable sot
    WHERE yt.ID = sot.ID
    )

Also, good article at SELECT 1 vs SELECT * – An Interesting Observation