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12 lines
1.2 KiB
SQL
12 lines
1.2 KiB
SQL
mysql> CREATE TABLE t1 (i INT);
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mysql> explain select * from t1 where not exists ((select t11.i from t1 t11) union (select t12.i from t1 t12));
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+----+--------------+------------+--------+---------------+------+---------+------+------+--------------------------------+
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| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
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+----+--------------+------------+--------+---------------+------+---------+------+------+--------------------------------+
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| 1 | PRIMARY | t1 | system | NULL | NULL | NULL | NULL | 0 | const row not found |
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| 2 | SUBQUERY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used |
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| 3 | SUBQUERY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | no matching row in const table |
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| 4 | UNION | t12 | system | NULL | NULL | NULL | NULL | 0 | const row not found |
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| NULL | UNION RESULT | <union2,4> | ALL | NULL | NULL | NULL | NULL | NULL | |
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+----+--------------+------------+--------+---------------+------+---------+------+------+--------------------------------+
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