drop命令会把索引也删掉,某些时候只想清空数据,索引要保留.所以使用下面的方式清空

>use db名称
<'switched to db xxx'
>db.集合名称.deleteMany({})
<{ acknowledged: true, deletedCount: 24 }

例如要清空数据库facebook中user集合的所有数据

>use facebook
<'switched to db facebook'
>db.facebook.deleteMany({})
<{ acknowledged: true, deletedCount: 24 }

也可以加条件,删除所有name是张三的数据

>use facebook
<'switched to db facebook'
>db.facebook.deleteMany({"name":"张三"})
<{ acknowledged: true, deletedCount: 6 }