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create table t1_outerjoin(a int, b int , c int); create table t2_outerjoin(a int); create table t3_outerjoin(a int, b int); create table t4_outerjoin(a int); SELECT * FROM t1_outerjoin ... 阅读全文
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当然是在折腾了很长时间之后 阅读全文
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explain extended select count(*) from (select id from states where country_id 10 and name='aaa')) t; +----+--------------+------------+-------+---------------+---------+---------+------+------+-----... 阅读全文
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QUERY: explain extended select id from states where country_id 10) TRACE: { "steps": [ { "join_preparation": { "select#": 1, "steps": [ ... 阅读全文
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mysql> explain extended select * from cities where id in (select phonecode from countries group by name); +----+-------------+-----------+--------+---------------+---------+---------+--------------... 阅读全文
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explain select `countries`.`id` AS `id`,`countries`.`sortname` AS `sortname`,`countries`.`name` AS `name`,`countries`.`phonecode` AS `phonecode` from 阅读全文