Question

I was reading a SQL “cookbook” type reference, and I came across a statement that I has never come across before:

INSERT INTO table (col1, col2)
SELECT t.col1, 8
FROM table AS t
WHERE t.col2 = 5
UNION ALL
SELECT 8, 8

Now what confuses me is a number (in this example, 8) immediately following the SELECT statement. In my limited SQL experience, I have only come across SELECT queries that are followed by column names. Could somebody help me understand what this does? Thanks!

Answer 1

The SELECT 8, 8 does exactly what it appears to do; it returns a result set with 2 un-named columns each containing 8 – if you run just that statement yourself you’ll see exactly that.

You are free to select literal values & expressions just as you are columns, function results etc;

SELECT 'cake', 123 + 456

The UNION ALL merges (non-duplicate) rows from the 1st table select with the result of the 2nd select so your inserting a single additional (8,8) row into the table.