$elemMatch

    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。

    2. > db.sample.employee.insert( { "id": 2, "content": [ { "name": "Tom", "phone": "456", "address": "2000 Market Street, Philadelphia" } ] } )
    3. > db.sample.employee.insert( { "id": 3, "content": { "name": "Septem", "phone": "789", "address": { "addr1": "3000 Market Street, Philadelphia", "addr2": "4000 Market Street, Philadelphia" } } } )
    4. > db.sample.employee.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",
    25.     }
    26.   ]
    27. }
    28. {
    29.   "_id": {
    30.     "$oid": "5aaa25ee48bcff191e000002"
    31.   },
    32.   "id": 3,
    33.   "content": {
    34.     "name": "Septem",
    35.     "phone": "789",
    36.     "address": {
    37.       "addr1": "3000 Market Street, Philadelphia",
    38.       "addr2": "4000 Market Street, Philadelphia"
    39.     }
    40.   }
    41. }
    42. Return 3 row(s).

    SequoiaDB shell 运行如下：

    • 数组匹配：

      1. > db.sample.employee.find( { "content": { $elemMatch: { "name": "Tom", "phone": "456" } } } )
      2. {
      3.   "_id": {
      4.     "$oid": "5822868a2b4c38286d000008"
      5.   },
      6.   "content": [
      7.     {
      8.       "name": "Tom",
      9.       "phone": "456",
      10.       "address": "2000 Market Street, Philadelphia"
      11.     }
      12.   ]
      13. }
      14. Return 1 row(s).

    • 使用“$regex”匹配符以及嵌套的“$elemMatch”匹配符：

      1. > db.sample.employee.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. }