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Click EMPLOYEESAVG(平均值)和 SUM (合计)函数组函数与空值…SELECT department_id AVG(salary)FROM employeesGROUP BY department_id …不能在 WHERE 子句中使用组函数可以在HAVING 子句中使用组函数过滤分组: HAVING 子句显示平均工资的最大值
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Click 例如:BSELECT employee_id job_idFROM employeesUNIONSELECT employee_id job_idFROM job_history显示所有曾经从事过与现在相同工作的雇员的雇员ID和职务 employee_idjob_idFROM employeesMINUSSELECT employee_idjob_idFROM job_
结束本节课后应当完成如下的目标:写一个多列的子查询描述和解释当子查询查到空值时其处理方法是什么在FROM子句中写一个子查询从多行多列返回值SQL> SELECT ordid prodid qty 2 FROM item 3 WHERE prodid IN (SELECT prodid 4 FROM item 5
Retrieving Data Using the SQL SELECT StatementObjectivesAfterpleting this lesson, you should be able to do the following:List the capabilities of SQL SELECT statementsExecute a basic SELECT state
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客户实例归档日志Handle共享池尺寸:SHARED_POOL_SIZE 库高速缓存:存放SQL语句文本解析代码和执行计划数据字典高速缓存:包含表列定义以及权限信息PGA库高速缓存数据库回滚段实例LGWRwanghailiang1练习一
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