此SQL查询是否创建临时表？

Question

SELECT *
FROM (
        (SELECT table1.id1, table1.id1_type AS id1,
         FROM child AS table2 STRAIGHT_JOIN parent AS table1 ON table1.id1=table2.id1
         AND table1.id2=table2.id2
         AND table1.time=table2.time
         WHERE table1.id1=123456
           AND ((table1.time>=0
                 AND table1.time<=1361936895)))
      UNION ALL
        (SELECT table1.id1 AS id1, table1.id1_type
         FROM child AS table2 STRAIGHT_JOIN step_parent AS table1 ON table1.id1=table2.id1
         AND table1.id2=table2.id2
         AND table1.time=table2.time
         WHERE table1.id1=123456
                 AND table1.time<=1361936895)))) AS T
WHERE id1_type NOT IN (15)
ORDER BY time DESC LIMIT 2000

Answer 1

这取决于数据库引擎来决定它认为什么是实现查询的最佳策略。假脱机到临时表绝对是它的选项之一。

表别名真的不应该与它有任何关系，正确的列就是正确的列，无论您为它使用什么标签。

出于兴趣，您尝试使用join而不是streat_join吗？您可以通过指定streak_join来限制查询优化器的选项。