子查询可以嵌套在FROM子句中多少级别？ [英] How many levels can subqueries be nested in a FROM clause?

问题描述

子句点可以嵌套在FROM子句中多少级别？

How many levels can subqueries be nested in a FROM clause?

推荐答案

根据Microsoft的限制为32级 [ ^ ]。



Oracle的相同限制是 255 [ ^ ]。



如果您正在使用其他数据库，则需要更新您的问题并说明您正在使用的数据库。

According to Microsoft the limit is 32 levels[^] for SQLServer.

Same limit in Oracle is 255[^].

If you're using some other DB you'll need to update your question and state what database you're using.

根据Microsoft的说法，没有技术限制 - http://technet.microsoft.com/en-us/library/ms177501(v = sql.105）.aspx [ ^ ]

但是任何新的嵌套级别会引入性能问题，所以请仔细考虑......

According to Microsoft there is no technical limit - http://technet.microsoft.com/en-us/library/ms177501(v=sql.105).aspx[^]
However with any new nested level you introduce a performance problem, so think carefully...

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