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

问题描述

显式和隐式内部连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;

对比

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

推荐答案

在性能方面，它们完全相同(至少在 SQL Server 中).

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

PS:请注意，IMPLICIT OUTER JOIN 语法自 SQL Server 2005 起已弃用.(问题中使用的 IMPLICIT INNER JOIN 语法仍受支持)

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)

弃用旧式"JOIN 语法:只有部分内容

这篇关于显式与隐式 SQL 连接的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！