19. Video: DISTINCT

DISTINCT is always used in SELECT statements, and it provides the unique rows for all columns written in the SELECT statement. Therefore, you only use DISTINCT once in any particular SELECT statement.

You could write:

SELECT DISTINCT column1, column2, column3
FROM table1;

which would return the unique (or DISTINCT) rows across all three columns.

You would not write:

SELECT DISTINCT column1, DISTINCT column2, DISTINCT column3
FROM table1;

You can think of DISTINCT the same way you might think of the statement "unique".

DISTINCT - Expert Tip

It’s worth noting that using DISTINCT, particularly in aggregations, can slow your queries down quite a bit.