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常见问题及解答(FAQ)
版本信息
{ <字段名>: { $et: <值> } }
指定相等条件,$et 匹配符匹配记录中某个字段的值等于指定的值。
在集合 sample.employee 插入如下记录:
> db.sample.employee.insert( { "id": 1, "item": { "name": "Tom", "code": "123" } } )
> db.sample.employee.insert( { "id": 2, "item": { "name": "Jack", "code": "123" } } )
> db.sample.employee.insert( { "id": 3, "item": { "name": "Mike", "code": "456" } } )
> db.sample.employee.insert( { "id": 4, "item": { "name": "Lucy", "code": "789" }, "phone": [ "135", "177" ] } )
查询 id 字段值等于 1 的记录
> db.sample.employee.find( { "id": { "$et": 1 } } )
{
"_id": {
"$oid": "5822b0472b4c38286d000009"
},
"id": 1,
"item": {
"name": "Tom",
"code": "123"
}
}
查询相当于:
> db.sample.employee.find( { "id": 1 } )
匹配嵌套字段 name 的值等于“Jack”的记录
> db.sample.employee.find( { "item.name": { "$et": "Jack" } } )
{
"_id": {
"$oid": "5822b04b2b4c38286d00000a"
},
"id": 2,
"item": {
"name": "Jack",
"code": "123"
}
}
Return 1 row(s).
查询相当于:
> db.sample.employee.find( { "item.name": "Jack" } )
匹配数组元素
> db.sample.employee.find( { "phone": { "$et": "135" } } )
{
"_id": {
"$oid": "5822b0562b4c38286d00000c"
},
"id": 4,
"item": {
"name": "Lucy",
"code": "789"
},
"phone": [
"135",
"177"
]
}
Return 1 row(s).
查询相当于:
> db.sample.employee.find( { "phone": "135" } )