select * from A表 a left join B表 b on a.id=b.a_id and b.字段='/*条件*/' ; 可查出左表所有数据 select * from A表 a left join B表 b on a.id=b.a_id where b.字段='/*条件*/' ; 只能查出部分数据
在C#中,如果要实现两个列表的左链接查询,我们的一般用法就是用的linq表达式就是 List<Pet> pets = }, }, } }; List<Pet2> pets2 = new List<Pet2>{ new Pet2 { Name="Barley", Sex = "男" }, new Pet2 { Name="Boots", Sex = "男"}, }; var list2 = f
var query = from t0 in context.ExpressSendMaster join t1 in context.Supplier on t0.SupplierCode equals t1.SupplierCode join t2 in context.ExpressSendPackageRule on t0.AreaId equals t2.Id into t0_join from t0_t2 in t0_join.DefaultIfEmpty() where t0.Id
declare @pageIndex int -- 第几页 declare @pageSize int -- 每页包含的记录数 --这里注意一下,不能直接把变量放在这里,要用select select top (select @pageSize) * from ( SELECT ROW_NUMBER() over(order by 学号) as rownumber, GHO总表.学号, GHO总表.姓名, 手机号码 FROM [GHO总表],A1基本信息表 ' and 专业= '法学' and
mysql数据库优化课程---12.mysql嵌套和链接查询 一.总结 一句话总结:查询user表中存在的所有班级的信息? in distinct mysql> select * from class where id in(select distinct class_id from user);+----+--------+------------+| id | name | ctime |+----+--------+------------+| 1 | class1 | 1
SQL左链接LEFT JOIN关键字返回左表(表1)中的所有行,即使在右表(表2)中没有匹配.如果在正确的表中没有匹配,结果是NULL. SQL LEFT JOIN 语法 SELECT _column_name(s)_ FROM _table1_ LEFT JOIN _table2_ ON _table1.column_name_ = _table2.column_name_ ; 或: SELECT _column_name(s)_ FROM _table1_ LEFT OUTER JOIN _
Linq to SQL 语法查询(链接查询,子查询 & in操作 & join,分组统计等) 子查询 描述:查询订单数超过5的顾客信息 查询句法: var 子查询 = from c in ctx.Customers where (from o in ctx.Orders group o by o.CustomerID into o where o.Count() > 5 select o.Key).Contains(c.CustomerID) select c; in 操作 描述:查
