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MongoDB数据库查询实例分析与操作指南

1. 数据库基础查询

1.1 记录总数统计

db.comment.count()

返回结果：5

1.2 用户ID查询

db.comment.count({userid: "1003"})

返回结果：2

2. 分页查询

2.1 查询前两条记录

db.comment.find().limit(2)

返回结果：

{    "_id": "1",     "articleid": "100001",     "content": "我们不应该把清晨浪费在手机上，健康很重要，一杯温水幸福你我他。",    "userid": "1002",     "nickname": "相忘于江湖",     "createdatetime": ISODate("1970-01-01T00:00:00Z"),     "likenum": 1000,     "state": "1"}{    "_id": "2",     "articleid": "100001",     "content": "我夏天空腹喝凉开水，冬天喝温开水",    "userid": "1005",     "nickname": "伊人憔悴",     "createdatetime": ISODate("2019-08-05T23:58:51.485Z"),     "likenum": 888,     "state": "1"}

2.2 跳过前两条记录，查询两条记录

db.comment.find().limit(2).skip(2)

返回结果：

{    "_id": "3",     "articleid": "100001",     "content": "我一直喝凉开水，冬天夏天都喝。",    "userid": "1004",     "nickname": "杰克船长",     "createdatetime": ISODate("2019-08-06T01:05:06.321Z"),     "likenum": 666,     "state": "1"}{    "_id": "4",     "articleid": "100001",     "content": "专家说不能空腹吃饭，影响健康。",    "userid": "1003",     "nickname": "凯撒",     "createdatetime": ISODate("2019-08-06T08:18:35.288Z"),     "likenum": 2000,     "state": "1"}

2.3 跳过前四条记录，查询第五条

db.comment.find().limit(2).skip(4)

返回结果：

{    "_id": "5",     "articleid": "100001",     "content": "研究表明，刚烧开的水千万不能喝，因为烫嘴。",    "userid": "1003",     "nickname": "凯撒",     "createdatetime": ISODate("1970-01-01T00:00:00Z"),     "likenum": 3000,     "state": "1"}

3. 排序查询

3.1 按用户ID升序排列

db.comment.find().sort({userid: 1})

返回结果：

{    "_id": "1",     "userid": "1002"}{    "_id": "4",     "userid": "1003"}{    "_id": "5",     "userid": "1003"}{    "_id": "3",     "userid": "1004"}{    "_id": "2",     "userid": "1005"}

3.2 投影查询（仅 userid），按用户ID升序排列

db.comment.find({},{userid: 1}).sort({userid: 1})

返回结果：

{    "_id": "1",     "userid": "1002"}{    "_id": "4",     "userid": "1003"}{    "_id": "5",     "userid": "1003"}{    "_id": "3",     "userid": "1004"}{    "_id": "2",     "userid": "1005"}

3.3 按用户ID降序排列

db.comment.find({},{userid: 1}).sort({userid: -1})

返回结果：

{    "_id": "2",     "userid": "1005"}{    "_id": "3",     "userid": "1004"}{    "_id": "4",     "userid": "1003"}{    "_id": "5",     "userid": "1003"}{    "_id": "1",     "userid": "1002"}

4. 复杂查询

4.1 查询包含“开水”的内容

db.comment.find({content: /开水/})

返回结果：

{    "_id": "2",     "articleid": "100001",     "content": "我夏天空腹喝凉开水，冬天喝温开水",    "userid": "1005",     "nickname": "伊人憔悴",     "createdatetime": ISODate("2019-08-05T23:58:51.485Z"),     "likenum": 888,     "state": "1"}{    "_id": "3",     "articleid": "100001",     "content": "我一直喝凉开水，冬天夏天都喝。",    "userid": "1004",     "nickname": "杰克船长",     "createdatetime": ISODate("2019-08-06T01:05:06.321Z"),     "likenum": 666,     "state": "1"}

5. 比较查询

5.1 查询点赞数量大于 700 的记录

db.comment.find({likenum: { $gt: NumberInt(700) }})

返回结果：

{    "_id": "1",     "articleid": "100001",     "content": "我们不应该把清晨浪费在手机上，健康很重要，一杯温水幸福你我他。",    "userid": "1002",     "nickname": "相忘于江湖",     "createdatetime": ISODate("1970-01-01T00:00:00Z"),     "likenum": 1000,     "state": "1"}{    "_id": "2",     "articleid": "100001",     "content": "我夏天空腹喝凉开水，冬天喝温开水",    "userid": "1005",     "nickname": "伊人憔悴",     "createdatetime": ISODate("2019-08-05T23:58:51.485Z"),     "likenum": 888,     "state": "1"}{    "_id": "4",     "articleid": "100001",     "content": "专家说不能空腹吃饭，影响健康。",    "userid": "1003",     "nickname": "凯撒",     "createdatetime": ISODate("2019-08-06T08:18:35.288Z"),     "likenum": 2000,     "state": "1"}{    "_id": "5",     "articleid": "100001",     "content": "研究表明，刚烧开的水千万不能喝，因为烫嘴。",    "userid": "1003",     "nickname": "凯撒",     "createdatetime": ISODate("1970-01-01T00:00:00Z"),     "likenum": 3000,     "state": "1"}

6. 包含查询

6.1 查询包含 userid 为 1003 或 1004 的记录

db.comment.find({userid: { $in: ["1003", "1004"] }})

返回结果：

{    "_id": "3",     "articleid": "100001",     "content": "我一直喝凉开水，冬天夏天都喝。",    "userid": "1004",     "nickname": "杰克船长",     "createdatetime": ISODate("2019-08-06T01:05:06.321Z"),     "likenum": 666,     "state": "1"}{    "_id": "4",     "articleid": "100001",     "content": "专家说不能空腹吃饭，影响健康。",    "userid": "1003",     "nickname": "凯撒",     "createdatetime": ISODate("2019-08-06T08:18:35.288Z"),     "likenum": 2000,     "state": "1"}{    "_id": "5",     "articleid": "100001",     "content": "研究表明，刚烧开的水千万不能喝，因为烫嘴。",    "userid": "1003",     "nickname": "凯撒",     "createdatetime": ISODate("1970-01-01T00:00:00Z"),     "likenum": 3000,     "state": "1"}

7. 条件连接查询

7.1 查询 likenum 大于等于 700 并且小于 2000 的记录

db.comment.find({ $and: [{likenum: { $gte: NumberInt(700) }}, {likenum: { $lt: NumberInt(2000) }}] })

返回结果：

{    "_id": "1",     "articleid": "100001",     "content": "我们不应该把清晨浪费在手机上，健康很重要，一杯温水幸福你我他。",    "userid": "1002",     "nickname": "相忘于江湖",     "createdatetime": ISODate("1970-01-01T00:00:00Z"),     "likenum": 1000,     "state": "1"}{    "_id": "2",     "articleid": "100001",     "content": "我夏天空腹喝凉开水，冬天喝温开水",    "userid": "1005",     "nickname": "伊人憔悴",     "createdatetime": ISODate("2019-08-05T23:58:51.485Z"),     "likenum": 888,     "state": "1"}

7.2 查询 userid 为 1003 或点赞数小于 1000 的记录

db.comment.find({ $or: [{userid: "1003"}, {likenum: { $lt: NumberInt(1000) }}] })

返回结果：

{    "_id": "2",     "articleid": "100001",     "content": "我夏天空腹喝凉开水，冬天喝温开水",    "userid": "1005",     "nickname": "伊人憔悴",     "createdatetime": ISODate("2019-08-05T23:58:51.485Z"),     "likenum": 888,     "state": "1"}{    "_id": "3",     "articleid": "100001",     "content": "我一直喝凉开水，冬天夏天都喝。",    "userid": "1004",     "nickname": "杰克船长",     "createdatetime": ISODate("2019-08-06T01:05:06.321Z"),     "likenum": 666,     "state": "1"}{    "_id": "4",     "articleid": "100001",     "content": "专家说不能空腹吃饭，影响健康。",    "userid": "1003",     "nickname": "凯撒",     "createdatetime": ISODate("2019-08-06T08:18:35.288Z"),     "likenum": 2000,     "state": "1"}{    "_id": "5",     "articleid": "100001",     "content": "研究表明，刚烧开的水千万不能喝，因为烫嘴。",    "userid": "1003",     "nickname": "凯撒",     "createdatetime": ISODate("1970-01-01T00:00:00Z"),     "likenum": 3000,     "state": "1"}

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