useRef获取DOM 组件通讯 子传父
function Son({ onGetMsg }){const sonMsg this is son msgreturn (<div>{/* 在子组件中执行父组件传递过来的函数 */}<button onClick{()>onGetMsg(sonMsg)}>send</button></div>)
}function App(){const getMsg…
文章目录 yq命令快速 Recipes查找数组中的项目查找并更新数组中的项目深度修剪一棵树对数组中的项目进行多次或复杂的更新按字段对数组进行排序 OperatorsDeleteDelete entry in mapDelete nested entry in mapDelete entry in arrayDelete nested entry in arrayDelete no mat…
11、取得最后入职的5名员工
select ename from emp order by hiredate desc limit 5;
12、取得每个薪水等级有多少员工 先取每个员工的薪水等级
Select e.ename,s.grade grade
From emp e
Join salgrade s
On e.sal between s.losal and s.hisal 接着直接分组求
Select …