• $elemMatch
    • 语法
    • 描述
    • 示例

    $elemMatch

    语法

    1. { <字段名>: { $elemMatch: { <子字段名>: <表达式>, ... } } }

    描述

    选择集合中“<字段名>”匹配指定“{ <子字段>: <表达式> … }”的记录。

    其中“<表达式>”可以是值，也可以是带有匹配符的表达式，“$elemMatch”匹配符支持多层嵌套。

    示例

    在集合 foo.bar 中插入 3 条记录：

    1. > db.foo.bar.insert( { "id": 1, "content": { "name": "Jack", "phone": "123", "address": "1000 Market Street, Philadelphia" } } )
    2. > db.foo.bar.insert( { "id": 2, "content": [ { "name": "Tom", "phone": "456", "address": "2000 Market Street, Philadelphia" } ] } )
    3. > db.foo.bar.insert( { "id": 3, "content": { "name": "Septem", "phone": "789", "address": { "addr1": "3000 Market Street, Philadelphia", "addr2": "4000 Market Street, Philadelphia" } } } )
    4. > db.foo.bar.find()
    5. {
    6.   "_id": {
    7.     "$oid": "5a73ce416a3e18f64e000010"
    8.   },
    9.   "id": 1,
    10.   "content": {
    11.     "name": "Jack",
    12.     "phone": "123",
    13.     "address": "1000 Market Street, Philadelphia"
    14.   }
    15. }
    16. {
    17.   "_id": {
    18.     "$oid": "5a73ce476a3e18f64e000011"
    19.   },
    20.   "id": 2,
    21.   "content": [
    22.     {
    23.       "name": "Tom",
    24.       "phone": "456",
    25.       "address": "2000 Market Street, Philadelphia"
    26.     }
    27.   ]
    28. }
    29. {
    30.   "_id": {
    31.     "$oid": "5aaa25ee48bcff191e000002"
    32.   },
    33.   "id": 3,
    34.   "content": {
    35.     "name": "Septem",
    36.     "phone": "789",
    37.     "address": {
    38.       "addr1": "3000 Market Street, Philadelphia",
    39.       "addr2": "4000 Market Street, Philadelphia"
    40.     }
    41.   }
    42. }
    43. Return 3 row(s).

    SequoiaDB shell 运行如下：

    • 嵌套对象匹配：
    1. > db.foo.bar.find( { "content": { $elemMatch: { "name": "Jack", "phone": "123" } } } )
    2. {
    3.   "_id": {
    4.     "$oid": "5822868a2b4c38286d000007"
    5.   },
    6.   "id": 1,
    7.   "content": {
    8.     "name": "Jack",
    9.     "phone": "123",
    10.     "address": "1000 Market Street, Philadelphia"
    11.   }
    12. }
    13. Return 1 row(s).
    • 数组匹配：
    1. > db.foo.bar.find( { "content": { $elemMatch: { "name": "Tom", "phone": "456" } } } )
    2. {
    3.   "_id": {
    4.     "$oid": "5822868a2b4c38286d000008"
    5.   },
    6.   "id": 2,
    7.   "content": [
    8.     {
    9.       "name": "Tom",
    10.       "phone": "456",
    11.       "address": "2000 Market Street, Philadelphia"
    12.     }
    13.   ]
    14. }
    15. Return 1 row(s).
    • 匹配“content”字段中子字段“phone”符合表达式“ $lte："123" ”的记录：
    1. > db.foo.bar.find( { content: { $elemMatch: { "phone" : { $lte : "123" } } } } )
    2. {
    3. "_id": {
    4.   "$oid": "5a0106e51f9b983f4600000b"
    5. },
    6. "id": 1,
    7. "content": {
    8.   "name": "Jack",
    9.   "phone": "123",
    10.   "address": "1000 Market Street, Philadelphia"
    11. }
    12. }
    13. Return 1 row(s).
    • 使用“$regex”匹配符以及嵌套的“$elemMatch”匹配符：
    1. > db.foo.bar.find( { "content" : { $elemMatch : { address : { $elemMatch: { addr1 : { $regex : ".*Philadelphia$" } } } } } } )
    2. {
    3. "_id": {
    4.   "$oid": "5a0107641f9b983f4600000d"
    5. },
    6. "id": 3,
    7. "content": {
    8.   "name": "Septem",
    9.   "phone": "789",
    10.   "address": {
    11.     "addr1": "3000 Market Street, Philadelphia",
    12.     "addr2": "4000 Market Street, Philadelphia"
    13.   }
    14. }
    15. }
    16. Return 1 row(s).