Selecting two tables where the columns are not always equal
Posted: Mon Aug 18, 2008 10:43 am
Hello,
I have a few tables with various fields I need to update so I am making a view that will be updated to handle where each column is for me.
So the join is on two columns:
enc_id and person_id
The layout needs to be like so:
This would be simple but tbl2 (b) doesn't always have either of those fields filled in.
So if they aren't empty, they will equal but if they are empty then it should just return NULL for that table's columns, right?
I get 0 results returned but if I leave of tbl2 completely I get tbl1 as expected.
How do I get it to join on the columns if the row exists in tbl2 and otherwise return NULL for that table?
I have a few tables with various fields I need to update so I am making a view that will be updated to handle where each column is for me.
So the join is on two columns:
enc_id and person_id
The layout needs to be like so:
Code: Select all
SELECT
a.col1, a.col2, a.col3,
b.col1, b.col2, b.col3
FROM
tbl1 a, tbl2 a
WHERE
a.enc_id = b.enc_id AND a.person_id = b.person_id
So if they aren't empty, they will equal but if they are empty then it should just return NULL for that table's columns, right?
I get 0 results returned but if I leave of tbl2 completely I get tbl1 as expected.
How do I get it to join on the columns if the row exists in tbl2 and otherwise return NULL for that table?