WHERE 子句中的列顺序重要吗? [英] Does the order of columns in a WHERE clause matter?

问题描述

WHERE 子句中列的顺序会影响性能吗?

Does the order of the columns in a WHERE clause effect performance?

例如

假设我将具有更高独特性潜力的列放在首位，反之亦然?

Say I put a column that has a higher potential for uniqueness first or visa versa?

推荐答案

如果有一个不错的查询优化器:它不应该.

With a decent query optimiser: it shouldn't.

但在实践中，我怀疑它可能.

But in practice, I suspect it might.

您只能通过测量来判断您的情况.并且测量值可能会随着数据库中数据分布的变化而变化.

You can only tell for your cases by measuring. And the measurements will likely change as the distribution of data changes in the database.

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