sql語句之分組，聚合函式

1.背景：作為一名測試工程師，sql語句也是必備技能，剛好前兩天朋友的面試題做為列子簡單做下筆記

2.question：

3.answer：

1）update employee set salary=salary+200 where age>=40 and salary<2000

2)select distinct depart.name,count(depart.id) as m from depart ,employee,DE where employee.ID=DE.eid and depart.id=DE.did and employee.age>=40 and employee.salary<2200 GROUP BY(depart.name) order by  m

4.提示：個人覺得sql語句並不難，格外要注意的是各個語句的執行順序，推薦大家看下這篇部落格寫的很詳細

https://www.cnblogs.com/ghost-xyx/p/3811036.html

~還有左聯、外聯、跨表聯