具有大量 JOIN 条件的 SQL 查询非常慢

Question

我继承了一个 SQL Server 2008 R2 项目，其中包括从另一个表更新表:

• Table1(大约 150,000 行)有 3 个电话号码字段(Tel1、Tel2、Tel3)
• Table2(大约 20,000 行)有 3 个电话号码字段(Phone1、Phone2、Phone3)

.. 当这些数字中的任何一个匹配时，Table1 应该被更新。

当前代码如下:

UPDATE t1
SET surname = t2.surname, Address1=t2.Address1, DOB=t2.DOB, Tel1=t2.Phone1, Tel2=t2.Phone2, Tel3=t2.Phone3,
FROM Table1 t1 
inner join Table2 t2
on
(t1.Tel1 = t2.Phone1 and t1.Tel1 is not null) or
(t1.Tel1 = t2.Phone2 and t1.Tel1 is not null) or
(t1.Tel1 = t2.Phone3 and t1.Tel1 is not null) or
(t1.Tel2 = t2.Phone1 and t1.Tel2 is not null) or
(t1.Tel2 = t2.Phone2 and t1.Tel2 is not null) or
(t1.Tel2 = t2.Phone3 and t1.Tel2 is not null) or
(t1.Tel3 = t2.Phone1 and t1.Tel3 is not null) or
(t1.Tel3 = t2.Phone2 and t1.Tel3 is not null) or
(t1.Tel3 = t2.Phone3 and t1.Tel3 is not null);

但是，此查询需要 30 多分钟才能运行。

执行计划表明主要瓶颈是 Table1 上聚集索引扫描周围的嵌套循环。两个表的 ID 列都有聚簇索引。

由于我的 DBA 技能非常有限，任何人都可以建议提高此查询性能的最佳方法吗？将 Tel1、Tel2 和 Tel3 的索引添加到每一列是否是最佳举措，或者是否可以更改查询以提高性能？

Answer 1

乍一看，我建议从选择中删除所有 OR 条件。

看看这是否更快(它将您的更新转换为 3 个不同的更新):

UPDATE t1
SET surname = t2.surname, Address1=t2.Address1, DOB=t2.DOB, Tel1=t2.Phone1, Tel2=t2.Phone2, Tel3=t2.Phone3,
FROM Table1 t1 
inner join Table2 t2
on
(t1.Tel1 is not null AND t1.Tel1 IN (t2.Phone1, t2.Phone2, t2.Phone3);

UPDATE t1
SET surname = t2.surname, Address1=t2.Address1, DOB=t2.DOB, Tel1=t2.Phone1, Tel2=t2.Phone2, Tel3=t2.Phone3,
FROM Table1 t1 
inner join Table2 t2
on
(t1.Tel2 is not null AND t1.Tel2 IN (t2.Phone1, t2.Phone2, t2.Phone3);

UPDATE t1
SET surname = t2.surname, Address1=t2.Address1, DOB=t2.DOB, Tel1=t2.Phone1, Tel2=t2.Phone2, Tel3=t2.Phone3,
FROM Table1 t1 
inner join Table2 t2
on
(t1.Tel3 is not null AND t1.Tel3 IN (t2.Phone1, t2.Phone2, t2.Phone3);