Mongodb - Introduction to the usage of logical operators not, and, or, nor in query statements

Come and learn today mongodb Usage of some other query statements in , It mainly contains the following contents :

1、 Logical operators $not

such as ： Inquire about user surface age Not for 18 The data of ：

db.user.find({age:{$ne:18}})
db.user.find({age:{$not:{$eq:18}}})

Be careful ： If the field to be queried does not exist , It will also count as a condition

2、 Logical operators $and

Such as query user surface name by “ Xiaobo ”, also age by 17 The data of

db.user.find({name:" Xiaobo ",age:17})
db.user.find({$and:[{name:" Xiaobo "},{age:17}]})

Be careful : $and The following must correspond to an array format , Otherwise, an error will be reported ：

3、 Logical operators $or

Such as query user In the table name by “ Xiaobo ” perhaps “ Test Xiaobo ” The data of ：

db.user.find({name:{$in:[' Xiaobo ',' Test Xiaobo ']}})
db.user.find({$or:[{name:{$eq:' Xiaobo '}},{name:{$eq:' Test Xiaobo '}}]})
db.user.find({$or:[{name:' Xiaobo '},{name:' Test Xiaobo '}]})

4、 Logical operators $nor

For the front $and、$or、$not Usage of , You may have seen it , But for the $nor operation , You may see less ,$nor The simple understanding is ： One of the conditions is not satisfied .

Such as query name Not for “ Xiaobo ” perhaps “ Test Xiaobo ” The data of ：

db.user.find({name:{$nin:[' Xiaobo ',' Test Xiaobo ']}})
db.user.find({$nor:[{name:' Xiaobo '},{name:' Test Xiaobo '}]})

Be careful ： If the field to be queried does not exist , It will also count as a condition

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