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Question

How to change the way that cols orders it self?

If we have a table like this

a        b        c
1        xx       xy
2        xy       yx
3        yy       xx

Since both of b and c are same type I would like to aggregate them in a one col call E respectively

a        E
1        xx
1        xy
2        xy
2        yx
3        yy
3        xx

Is that possible using MYSQL 5.7 ?

Answer 1

You can just do it with a UNION ALL (you may or may not need the ORDER BY part, depending on your use-case):

SELECT
    a, b as `E`
FROM
    a
UNION ALL 
SELECT
    a, c as `E`
FROM
    a 
ORDER BY
    a ;

You can check it here.