group by 销售日期)--通过”日期“的表左联连”销售“的表直接查询出我们要的数据 select a.销售日期,isnull(b.销售额,0)as销售额 from 日期 a Left Join 销售 bONa.销售日期=b.销售日期 实现效果 上面可以看出用With As我们直接省去了一个临时表的创建,而且通过With As定义了一个SQL的片断,让我们代码的...
WITH DirectReports(Name, Title, EmployeeID, EmployeeLevel, Sort) AS (SELECT CONVERT(varchar(255), c.FirstName + ' ' + c.LastName), e.Title, e.EmployeeID, 1, CONVERT(varchar(255), c.FirstName + ' ' + c.LastName) FROM HumanResources.Employee AS e JOIN Person.Contact AS c ON e....
WITH AS子句通常被称为“公用表表达式”(Common Table Expression,简称CTE)。它的一般语法如下: sql WITH cte_name AS ( -- 你的查询语句 SELECT ... ) SELECT ... FROM cte_name -- 可能还有其他的JOIN、WHERE等子句 下面是一个具体的例子,假设我们有一个名为employees的表,包含员工的id、name、departme...
SELECT*FROM(SELECT*FROMtable_a--想象这是这是一个语句很长、很复杂的子查询)ASaLEFTJOIN(SELECT*FROMtable_b--想象这是这是另一个语句很长、很复杂的子查询)ASbONa.a_id=b.a_idUNIONSELECT*FROM(SELECT*FROMtable_a--想象这是这是一个语句很长、很复杂的子查询)ASaLEFTJOIN(SELECT*FROMtable_b--想象...
以下示例特意创建了一个无限循环,然后使用MAXRECURSION提示将递归级别限制为两级WITHcte(EmployeeID,ManagerID,Title)as(SELECTEmployeeID,ManagerID,TitleFROMHumanResources.EmployeeWHEREManagerIDISNOTNULLUNIONALLSELECTcte.EmployeeID,cte.ManagerID,cte.TitleFROMcteJOINHumanResources.EmployeeASeONcte.ManagerID=e....
一.WITH AS的含义 WITH AS短语,也叫做子查询部分(subquery factoring),可以定义一个SQL片断,该SQL片断会被整个SQL语句用到。可以使SQL语句的可读性更高,也可以在UNION ALL的不同部分,作为提供数据的部分。对于UNION ALL,使用WITH AS定义了一个UNION ALL语句,当该片断被调用2次以上,优化器会自动将该WITH AS短语...
```sql WITH SalesDepartment AS ( SELECT employee_id, name FROM employees WHERE department = 'Sales' ), HighSalary AS ( SELECT employee_id, salary FROM salaries WHERE salary > 50000 ) SELECT s.name, h.salary FROM SalesDepartment s JOIN HighSalary h ON s.employee_id = h.employee_id; ...
with cte as ( select Id,Pid,DeptName,0 as lvl from Department where Id = 2 union all select d.Id,d.Pid,d.DeptName,lvl+1 from cte c inner join Department d on c.Id = d.Pid ) select * from cte WITH语句的优点:(1). SQL可读性增强。比如对于特定with子查询取个有意义的名字等。(2...
sql WITH DepartmentNames AS SELECT e.employee_id, e.employee_name, dn.department_name FROM employees e JOIN DepartmentNames dn ON e.employee_id = dn.employee_id;在这个例子中，我们首先使用WITH...AS语句创建了一个名为DepartmentNames的公共表表达式，该表达式通过连接employees表和departments...
filter消除,CBO将基于数据字典底层的基表重新组合,使执行计划变成hash joinanti,0.23秒便执行完成了。 下面我们再来看下通过with as materialize优化subquery unnesting的例子。 SQL如下: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 selectAREA_NAME,sum(reve)from t_order o ...