在数据库的世界里,SQL(结构化查询语言)是与数据交互的主要工具。SQL Server作为微软的一款关系数据库管理系统,广泛应用于企业的数据存储和管理中。在进行数据查询时,有时我们需要从多个表中获取信息,这时嵌套查询(Subquery)便发挥了重要的作用。本文将深入探讨SQL Server中的嵌套查询,包括它的用法、优缺点以及代码示例。
withxinxias(select incode,fname from tbSpXinXi where fname like'%茶'),kcas(select*from tbSpKc where1=1)select*from xinxi a,kc b where a.incode=b.incode 3. 如果With As的表达式名称与某个数据表或视图重名,则紧跟在该With As后面的SQL语句使用的仍然是With As的名称,当然,后面的SQL语句使用的...
SQL SERVER with递归示例一则 1WITHSUBQUERYAS( 2SELECT3ORGID4FROM5OM_ORGANIZATION6WHERE7PARENTORGID='ROOT' 8UNIONALL 9SELECT10B.ORGID11FROM12SUBQUERY A,13OM_ORGANIZATION B14WHERE15B.PARENTORGID=A.ORGID 16)SELECTDISTINCT17*18FROM19SUBQUERY
1 WITH SUBQUERY AS ( 2 SELECT 3 ORGID 4 FROM 5 OM_ORGANIZATION 6 WHERE 7 PARENTORGID = 'ROOT' 8 UNION ALL 9 SELECT 10 B.ORGID 11 FROM 12 SUBQUERY A, 13 OM_ORGANIZATION B 14 WHERE 15 B.PARENTORGID = A.ORGID 16 ) SELECT DISTINCT 17 * 18 FROM 19 SUBQUERY 1. 2. 3. 4. ...
For example, if SQL Server first examines the row for Syed Abbas, the variable Employee.BusinessEntityID takes the value 285, which SQL Server substitutes into the inner query. These two query samples represent a decomposition of the previous sample with the correlated subquery. SQL نسخ...
SQL Server 2008以后,表参数是可以用的。 例子: 首先,在新数据库MyDemo中创建新表 1: --创建新表 2: use MyDemo 3: CREATE TABLE [dbo].[Employees]( 4: [empid] [int] IDENTITY(1,1) NOT NULL, 5: [empname] [nvarchar](100) NULL, ...
subquery removal:主要是将AST转换为基于Apply算子的operator tree, nested loop language也可以解析成为这种方式。本步骤的详细讨论见第3节 apply算子转join算子,本步骤基于转换公式,将apply算子转换为join算子,实现子查询去关联(decorrelating),具体要根据apply算子的特征,生成相应的join,例如leftouter join、antijoin等,...
Applies to: SQL Server (starting with SQL Server 2016 (13.x) SP1), Azure SQL Database, and Azure SQL Managed Instance. Provides one or more extra hints to the query processor. The extra hints are specified with a hint nam...
Applies to: SQL Server (starting with SQL Server 2012 (11.x)). Prevents the query from using a nonclustered memory optimized columnstore index. If the query contains the query hint to avoid the use of the columnstore index, and an index hint to use a columnstore index, the hints are in...
Applies to: SQL Server (starting with SQL Server 2016 (13.x) SP1), Azure SQL Database, and Azure SQL Managed Instance. Provides one or more extra hints to the query processor. The extra hints are specified with a hint nameinside single quotation marks. ...