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26 lines
1.6 KiB
SQL
26 lines
1.6 KiB
SQL
explain
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select * from (
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select 1 as foo from sakila.actor as actor_1
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union
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select 1 from sakila.actor as actor_2
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) as der_1
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union
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select * from (
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select 1 as foo from sakila.actor as actor_3
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union all
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select 1 from sakila.actor as actor_4
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) as der_2;
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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 | <derived2> | system | NULL | NULL | NULL | NULL | 1 | |
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| 2 | DERIVED | actor_1 | index | NULL | PRIMARY | 2 | NULL | 200 | Using index |
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| 3 | UNION | actor_2 | index | NULL | PRIMARY | 2 | NULL | 200 | Using index |
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| NULL | UNION RESULT | <union2,3> | ALL | NULL | NULL | NULL | NULL | NULL | |
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| 4 | UNION | <derived5> | ALL | NULL | NULL | NULL | NULL | 400 | |
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| 5 | DERIVED | actor_3 | index | NULL | PRIMARY | 2 | NULL | 200 | Using index |
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| 6 | UNION | actor_4 | index | NULL | PRIMARY | 2 | NULL | 200 | Using index |
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| NULL | UNION RESULT | <union5,6> | ALL | NULL | NULL | NULL | NULL | NULL | |
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| NULL | UNION RESULT | <union1,4> | ALL | NULL | NULL | NULL | NULL | NULL | |
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+----+--------------+------------+--------+---------------+---------+---------+------+------+-------------+
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