Self-joins on derived tables in mysql- do i need to repeat the subqueries?

Question

I've got to execute a self-joining sql statement on a derived table in mysql. The derived table involves a hairy subquery, and I'm wondering if there's any alternative to actually writing and executing it twice-

SELECT a.* FROM (my hairy subquery) AS a
  LEFT JOIN (my hairy subquery) AS a2 
    ON a.groupname = a2.groupname etc..

Answer 1

标准解决方案是使用 CTE，但 MySQL 尚不支持这些。替代方案是：

• 您可以将子查询放入视图中并自连接视图。
• 您可以创建一个临时表并用子查询的结果填充它。

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