如何提高查询性能

Question

我有一个永远旋转的查询。我是 DBA 方面的新手。我想知道处理此类问题的第一件事是什么？我看了执行计划 table 在 ClassCode 上只有 1 个非聚集索引。我使用这么多 ClassCode 的原因是因为在 SSRS 报告参数 @ClassCode 默认情况下将是多个值，超过 200 个。

SELECT  PolicyNumber 
FROM    tblClassCodesPlazaCommercial 
WHERE   PolicyNumber NOT IN (
                            SELECT  PolicyNumber 
                            FROM    tblClassCodesPlazaCommercial 
                            WHERE   ClassCode IN    (
                                                    33489,31439,41894,68189,01239,01199,68528,67139,68128,739889,
                                                    33428,5561,68428,01484,5281,67227,01184,50199,23528,33283,03228,
                                                    50499,41594,50427,5181,31484,03199,6481,68239,50439,68489,36127,    
                                                    50472,67128,23149,33439,03149,5452,23189,50228,01428,69183,50527,
                                                    67499,739189,50159,31183,33499,01283,33128,50239,6451,33159,
                                                    21199,67272,67127,69427,5451,23239,67199,67449,67189,01599,40228,
                                                    50184,5551,33299,7398,40179,40128,50139,7381,33199,50497,23428,33129,
                                                    738299,67149,40184,23128,69199,68499,50299,31449,40497,68169,67197,
                                                    5191,67259,5252,03489,67459,21299,5262,01181,03428,31483,68183,68228,
                                                    31199,40484,738199,03499,31499,40189,7382,67439,21527,50449,01427,
                                                    68199,5453,50528,36228,50259,68299,50227,23459,33528,40199,40427,
                                                    21289,42594,5283,34489,5251,21228,50197
                                                    ) 
                            )

Answer 1

使用条件聚合来做到这一点

SELECT  PolicyNumber 
FROM    tblClassCodesPlazaCommercial 
group by PolicyNumber
having count(case when ClassCode IN  (33489,31439,41894,..) then 1 end) = 0

Case 语句将为列表中存在的 ClassCode 生成 1，否则将生成 NULL。现在计数聚合将为每个 PolicyNumber 计数 1。通过设置 = 0 我们可以确保 PolicyNumber 在给定列表中不存在任何 ClassCode。

Count可以换成

SUM(case when ClassCode IN  (33489,31439,41894,..) then 1 else 0 end) = 0

Answer 2

首先要做的是为ClassCode 和PolicyNumber 添加索引。您可以向这些列添加非聚集索引。

添加索引后，确保运行它不止一次，以便 SQL 可以为您制定执行计划。

这一定会对您的查询有所帮助。

如何提高查询性能

How can I improve query performance

tsql

sql-server

execution-time

reporting-services

notin