SQL学习笔记八 索引,表连接,子查询,ROW_NUMBER
索引 经常要查询的语句,则给它建一个索引 表连接 select T_Oders as o join T_Customers as C on o.CustomerId = c.Id 子查询 单值子查询 单列多值子查询 ROW_NUMBER()函数 ROW_NUMBER() OVER(ORDER BY
索引 经常要查询的语句,则给它建一个索引 表连接 select T_Oders as o join T_Customers as C on o.CustomerId = c.Id 子查询 单值子查询 单列多值子查询 ROW_NUMBER()函数 ROW_NUMBER() OVER(ORDER BY
有一个查询如下: 实现代码如下: SELECT c.CustomerId, CompanyName FROM Customers c WHERE EXISTS( SELECT OrderID FROM Orders o WHERE o.CustomerID = cu.CustomerID)这里面的E
无论使用int还是varchar,对于Status的多选查询都是不易应对的。举例,常规思维下对CustomerStatus的Enum设置如下: 实现代码如下: [Serializable] public enum CustomerStatus { New = 0, Active = 1, Overd
测试过程如下:create table salesas select * from sh.sales;create table customersasselect * from sh.customers; create unique index CUST_ID_un on customers(CUS
以下程序直接通过Hibernate API批量更新CUSTOMERS表中年龄大于零的所有记录的AGE字段: tx = session.beginTransaction();Iterator customers=session.find("from Customer c where c.age>