Hi I'm sure there's query for this kind of operation, but I just can't seem to get it.
I have a table like this:
product_id | saved_by | deleted_by | accepted_by | published_by
-----------+----------+------------+-------------+-------------
1 | user1 | | user1 |
-----------+----------+------------+-------------+-------------
2 | | user2 | |
-----------+----------+------------+-------------+-------------
3 | user2 | | | user3
-----------+----------+------------+-------------+-------------
4 | | | user1 | user4
-----------+----------+------------+-------------+-------------
And I'm trying to create a query that would s开发者_如何学JAVAelect all the users in those fields distinctly resulting in something like this:
users
------
user1
user2
user3
user4
Any pointers?
First thing that comes to mind is to UNION the columns:
SELECT t.users
FROM
(
SELECT saved_by AS users
FROM table
UNION
SELECT deleted_by
FROM table
UNION
SELECT accepted_by
FROM table
UNION
SELECT published_by
FROM table
) AS t;
http://postgresql.org/docs/9.0/interactive/sql-select.html
As a side note if this data was normalized it would be much easier to get the data the way you want.
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