MySQL - How to convert columns to rows?
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P粉533898694 2023-07-24 23:17:01
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<p><br /></p> <pre class="brush:php;toolbar:false;">ID | a | b | c 1 | a1 | b1 | c1 2 | a2 | b2 | c2</pre> <p>How to reorganize rows into IDs, column headers, values? </p> <pre class="brush:php;toolbar:false;">1 | a1 | a 1 | b1 | b 1|c1|c 2 | a2 | a 2 | b2 | b 2 | c2 | c</pre> <p><br /></p>
P粉533898694
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P粉511896716

You are trying to reverse the data. MySQL does not have a reverse function, so you need to use a UNION ALL query to convert columns to rows:

select id, 'a' col, a value
from yourtable
union all
select id, 'b' col, b value
from yourtable
union all
select id, 'c' col, c value
from yourtable

See SQL Fiddle with Demo.

This can also be achieved using CROSS JOIN:

select t.id,
  c.col,
  case c.col
    when 'a' then a
    when 'b' then b
    when 'c' then c
  end as data
from yourtable t
cross join
(
  select 'a' as col
  union all select 'b'
  union all select 'c'
) c

See SQL Fiddle with Demo

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