Question 217884 in PostgreSQL Question posted in
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Postgresql – concatenation of sql results from multiple rows

Im trying to get all unique values out of two rows in a databank as a list. Using postgresql and python.

I use this sql query:

SELECT DISTINCT from,to FROM database;

I get this output

 from | to 
------+-----
 a    | b
 d    | c
 b    | a

And in python as: [('a', 'b'), ('d', 'c'), ('b', 'a')]

But i want the result:["a", "b", "d", "c"]

I know i can use python to get this result but is there a direct sql query for that?

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2

Answers


  1. Chosen as BEST ANSWER
    0

    I found a solution:

    SELECT to AS value FROM database UNION SELECT from FROM database;

    In postgresql the UNION operator already restricts to distinct elements if ALL is not added. The alias is used to ensure that the output table column is named "value".


  2. 0

    You can make an union and select unique elements from there:

    SELECT DISTINCT value
FROM (
    SELECT from AS value FROM database
    UNION ALL
    SELECT to AS value FROM database
);
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