Using EXCEPT clause in PostgreSQL

Question

I am trying to use the EXCEPT clause to retrieve data from table. I want to get all the rows from table1 except the one\'s that exist in tabl

Answer 1

Your query seems perfectly valid:

SELECT fk_id_tbl2 AS some_name
FROM   table1
EXCEPT  -- you may want to use EXCEPT ALL
SELECT pk_id
FROM   table2;

Column names are irrelevant to the query. Only data types must match. The output column name of your query is fk_id_tbl2, just because it's the column name in the first SELECT. You can use any alias.

What's often overlooked: the subtle differences between EXCEPT (which folds duplicates) and EXCEPT ALL - which keeps all individual unmatched rows. More explanation and other ways to do the same, some of them much more flexible:

• Select rows which are not present in other table

Details for EXCEPT in the manual.