Re: Select statement with except clause - Mailing list pgsql-sql

JORGE MALDONADO wrote

> How does the EXCEPT work? Do fields should be identical?
> I need the difference to be on the first 3 fields.

Except operates over the entire tuple so yes all fields are evaluated and,
if they all match, the row from the "left/upper" query is excluded.

If you need something different you can use some variation of:
IN
EXISTS
NOT IN
NOT EXISTS

with a sub-query (correlated or uncorrelated as your need dictates).

For example:

SELECT col1, col2, col3, sum(col4)
FROM tbl
WHERE (col1, col2, col3) NOT IN (SELECT col1, col2, col3 FROM tbl2) -- not
correlated
GROUP BY col1, col2, col3

SELECT col1, col2, col3, sum(col4)
FROM tbl
WHERE NOT EXISTS (
  SELECT 1 FROM tbl AS tbl2 WHERE --make sure to alias the sub-query table
if it matches the outer reference
  (tbl.col1, tbl.col2, tbl.col3) = (tbl2.col1, tbl2.col2, tbl2.col3)
) -- correlated; reference "tbl" within the query inside the where clause
GROUP BY col1, col2, col3

I do not follow your example enough to provide a more explicit
example/solution but this should at least help point you in the right
direction.

David J.









--
View this message in context: http://postgresql.1045698.n5.nabble.com/Select-statement-with-except-clause-tp5756658p5756661.html
Sent from the PostgreSQL - sql mailing list archive at Nabble.com.


--
Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-sql