显式与隐式SQL连接 [英] Explicit vs implicit SQL joins

问题描述

显式和隐式内部联接是否存在效率差异? 例如:

Is there any efficiency difference in an explicit vs implicit inner join? For example:

SELECT * FROM
table a INNER JOIN table b
ON a.id = b.id;

vs.

SELECT a.*, b.*
FROM table a, table b
WHERE a.id = b.id;

推荐答案

在性能方面，它们是完全相同的(至少在SQL Server中是这样).

Performance wise, they are exactly the same (at least in SQL Server).

PS:请注意，从SQL Server 2005开始不推荐使用IMPLICIT OUTER JOIN语法.(仍然支持问题中使用的IMPLICIT INNER JOIN语法)

PS: Be aware that the IMPLICIT OUTER JOIN syntax is deprecated since SQL Server 2005. (The IMPLICIT INNER JOIN syntax as used in the question is still supported)

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