id college1 college2 college3
1 abc xyz rst
Above is the input-
Looking for output:-
id college1 college2 college3
1 abc
1 xyz
1 rst
One method is simply union all
:
select id, college1 as college from t
union all
select id, college2 as college from t
union all
select id, college3 as college from t;
This requires scanning the table three times, which is usually fine. But if "t" is really a complicated query or really big table, there are more efficient approaches.
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