在 2016/5/6 15:45, haiwen zhu 写道:
Hi guys,
I have a table like this:
+----+-------+-------+
| id | col_a | col_b |
+----+-------+-------+
| 1 | a | b |
| 2 | a | b |
| 3 | a | c |
| 4 | a | c |
+----+-------+-------+
execute sql a:
select * from test where id not in (select id from (select id from test
group by col_a,col_b) as a);
can get result
+----+-------+-------+
| id | col_a | col_b |
+----+-------+-------+
| 2 | a | b |
| 4 | a | c |
+----+-------+-------+
while execute sql b:
select * from test where id not in (select id from (select * from test) as
a group by col_a,col_a);
get empty result.
I'm very confused with this, somebody has idea about why?
I tried in 10.1.13-MariaDB and mysql5.6.
in mysql 5.5.46, the second result I got was :
+----+-------+-------+
| id | col_a | col_b |
+----+-------+-------+
| 2 | a | b |
| 3 | a | c |
| 4 | a | c |
+----+-------+-------+
(:(
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