使用多个联合优化查询性能

Posted 2023-04-15

【中文标题】使用多个联合优化查询性能

【英文标题】：Optimize query performance with multiple union

【发布时间】：2019-08-16 05:30:47

【问题描述】：

我的要求是在选定的表格中搜索特定的文本。

但是对于某些列，所有表的结构都不同，我需要使用连接多个表来使用 ID 进行搜索，而对于某些列，我可以直接搜索数据

我可以使用下面的查询来实现上述要求，但是有什么方法可以优化查询并缩短查询时间

 SELECT A.id, 
       Concat(A.fname, ' ', A.lname) AS NAME, 
       A.category 
FROM   dbo.employeedetail A 
       LEFT JOIN dbo.combovalues B 
              ON A.department = B.id 
       LEFT JOIN dbo.combovalues C 
              ON A.designation = C.id 
       LEFT JOIN dbo.combovalues D 
              ON A.esilocation = D.id 
       LEFT JOIN dbo.combovalues E 
              ON A.grade = E.id 
       LEFT JOIN dbo.combovalues F 
              ON A.costcentre = F.id 
       LEFT JOIN dbo.combovalues G 
              ON A.branch = G.id 
       LEFT JOIN dbo.combovalues H 
              ON A.location = H.id 
       LEFT JOIN dbo.combovalues I 
              ON A.esidispensary = I.id 
       LEFT JOIN dbo.combovalues J 
              ON A.ptlocation = J.id 
WHERE  ( code LIKE '%maharashtra%' 
          OR fname LIKE '%maharashtra%' 
          OR lname LIKE '%maharashtra%' 
          OR mname LIKE '%maharashtra%' 
          OR fathername LIKE '%maharashtra%' 
          OR gender LIKE '%maharashtra%' 
          OR maritalstatus LIKE '%maharashtra%' 
          OR pfaccno LIKE '%maharashtra%' 
          OR esino LIKE '%maharashtra%' 
          OR panno LIKE '%maharashtra%' 
          OR metro LIKE '%maharashtra%' 
          OR address1 LIKE '%maharashtra%' 
          OR address2 LIKE '%maharashtra%' 
          OR place LIKE '%maharashtra%' 
          OR city LIKE '%maharashtra%' 
          OR pincode LIKE '%maharashtra%' 
          OR phoneno LIKE '%maharashtra%' 
          OR corr_address1 LIKE '%maharashtra%' 
          OR corr_address2 LIKE '%maharashtra%' 
          OR corr_place LIKE '%maharashtra%' 
          OR corr_city LIKE '%maharashtra%' 
          OR corr_phone LIKE '%maharashtra%' 
          OR corr_pincode LIKE '%maharashtra%' 
          OR email LIKE '%maharashtra%' 
          OR personalemail LIKE '%maharashtra%' 
          OR personalmobileno LIKE '%maharashtra%' 
          OR officemobileno LIKE '%maharashtra%' 
          OR uannumber LIKE '%maharashtra%' 
          OR B.combovalue LIKE '%maharashtra%' 
          OR C.combovalue LIKE '%maharashtra%' 
          OR D.combovalue LIKE '%maharashtra%' 
          OR E.combovalue LIKE '%maharashtra%' 
          OR F.combovalue LIKE '%maharashtra%' 
          OR G.combovalue LIKE '%maharashtra%' 
          OR H.combovalue LIKE '%maharashtra%' 
          OR I.combovalue LIKE '%maharashtra%' 
          OR J.combovalue LIKE '%MAHARASHTRA%' ) 
UNION 
SELECT A.employeeid, 
       Concat(D.fname, ' ', D.lname) AS NAME, 
       D.category 
FROM   dbo.customefielddetail A 
       LEFT JOIN dbo.employeeconfig C 
              ON A.customefieldname = C.fieldname 
                 AND C.dfield = 'N' 
                 AND C.celltype = 'D' 
       LEFT JOIN dbo.combovalues B 
              ON A.fieldvalue = Cast(B.id AS NVARCHAR(max)) 
                 AND B.fieldname = B.fieldname 
       LEFT JOIN dbo.employeedetail D 
              ON A.employeeid = D.id 
WHERE  B.combovalue LIKE '%maharashtra%' 
UNION 
SELECT A.employeeid, 
       Concat(D.fname, ' ', D.lname) AS NAME, 
       D.category 
FROM   dbo.customefielddetail A 
       LEFT JOIN dbo.employeedetail D 
              ON A.employeeid = D.id 
WHERE  A.fieldvalue LIKE '%maharashtra%' 

【问题讨论】：

您的like 条件不能使用索引。您是否在相关列上有全文索引，如果有，您可以使用 CONTAINS 查询。那么它应该真的很快

@juergend 全文搜索未启用

【参考方案1】：

您可以轻松实现的第一个优化是将UNION 替换为UNION ALL。请记住，UNION 隐式删除重复行。因此，如果您确信不会得到任何重复值，那么这种替换应该是一个很好的优化。

希望对你有帮助！