SQL Server : SELECT n FROM (VALUES(0),(0),(0),(0)) t(n)

Question

Am seeing this in a script

SELECT n FROM (VALUES(0),(0),(0),(0)) t(n)

I know what it does. It is returning a column called 'n' with 4 rows, each of whose value is 0. But, what does this mean? What is t(n), and what is 'n'?

Answer 1

It's a table value constructor. t being the alias for the table, n the column name. A better example might make it clearer;

SELECT 
    MyData.Column1, 
    MyData.Column2 
FROM (VALUES(1, 'Tom'),
            (2, 'Dick'),
            (3, 'Harry'),
            (4, 'Ermintrude')
      ) MyData(Column1, Column2)

returns

Column1     Column2
----------- ----------
1           Tom
2           Dick
3           Harry
4           Ermintrude