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PgSQL wants to implement all kinds of column sub query operations of MySQL

2022-04-23 08:29:00 【CSDN Q & A】

mysql You can use the front row of the subquery reference to calculate ：

select n0 * 3 as n1, (select n1 * 2) from (select 1 n0) t1

however postgresql How to achieve it ？ At present, it is known that it can only be nested to the next layer ; Direct reference, such as mysql Yes, it will prompt that you can't find n1 Column .

select *, (select n1 * 2) from (select n0 * 3 n1   from (select 1 n0) t1) t

But you know , Nesting multiple layers is very inconvenient , Statistics are hard to nest one alias at a time ; Just at the forefront of the citation , Such as mysql It's much more convenient .

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