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  • mongodb 和 mysql 的对照

    In addition to the charts that follow, you might want to consider the Frequently Asked Questions section for a selection of common questions about MongoDB.

    Executables

    The following table presents the MySQL/Oracle executables and the corresponding MongoDB executables.

     MySQL/OracleMongoDB
    Database Server mysqld/oracle mongod
    Database Client mysql/sqlplus mongo

    Terminology and Concepts

    The following table presents the various SQL terminology and concepts and the corresponding MongoDB terminology and concepts.

    SQL Terms/ConceptsMongoDB Terms/Concepts
    database database
    table collection
    row document or BSON document
    column field
    index index
    table joins embedded documents and linking

    primary key

    Specify any unique column or column combination as primary key.

    primary key

    In MongoDB, the primary key is automatically set to the _id field.
    aggregation (e.g. group by)

    aggregation framework

    See the SQL to Aggregation Framework Mapping Chart.

    Examples

    The following table presents the various SQL statements and the corresponding MongoDB statements. The examples in the table assume the following conditions:

    • The SQL examples assume a table named users.

    • The MongoDB examples assume a collection named users that contain documents of the following prototype:

      {
  _id: ObjectID("509a8fb2f3f4948bd2f983a0"),
  user_id: "abc123",
  age: 55,
  status: 'A'
}

    Create and Alter

    The following table presents the various SQL statements related to table-level actions and the corresponding MongoDB statements.

    SQL Schema StatementsMongoDB Schema StatementsReference
     
    CREATE TABLE users (
    id MEDIUMINT NOT NULL
        AUTO_INCREMENT,
    user_id Varchar(30),
    age Number,
    status char(1),
    PRIMARY KEY (id)
)

    Implicitly created on first insert operation. The primary key_id is automatically added if _id field is not specified.

    db.users.insert( {
    user_id: "abc123",
    age: 55,
    status: "A"
 } )

    However, you can also explicitly create a collection:

    db.createCollection("users")
    		See insert() andcreateCollection()for more information. 
    ALTER TABLE users
ADD join_date DATETIME

    Collections do not describe or enforce the structure of its documents; i.e. there is no structural alteration at the collection level.

    However, at the document level, update() operations can add fields to existing documents using the $set operator.

    db.users.update(
    { },
    { $set: { join_date: new Date() } },
    { multi: true }
)
    		See the Data Modeling Considerations for MongoDB Applications,update(), and $set for more information on changing the structure of documents in a collection. 
    ALTER TABLE users
DROP COLUMN join_date

    Collections do not describe or enforce the structure of its documents; i.e. there is no structural alteration at the collection level.

    However, at the document level, update() operations can remove fields from documents using the $unset operator.

    db.users.update(
    { },
    { $unset: { join_date: "" } },
    { multi: true }
)
    		See Data Modeling Considerations for MongoDB Applications,update(), and $unsetfor more information on changing the structure of documents in a collection. 
    CREATE INDEX idx_user_id_asc
ON users(user_id)

    db.users.ensureIndex( { user_id: 1 } )
    		See ensureIndex()and indexes for more information. 
    CREATE INDEX
       idx_user_id_asc_age_desc
ON users(user_id, age DESC)

    db.users.ensureIndex( { user_id: 1, age: -1 } )
    		See ensureIndex()and indexes for more information. 
    DROP TABLE users

    db.users.drop()
    		See drop() for more information.

    Insert

    The following table presents the various SQL statements related to inserting records into tables and the corresponding MongoDB statements.

    SQL INSERT StatementsMongoDB insert() StatementsReference
     
    INSERT INTO users(user_id,
                  age,
                  status)
VALUES ("bcd001",
        45,
        "A")

    db.users.insert( {
       user_id: "bcd001",
       age: 45,
       status: "A"
} )
    		See insert() for more information.

    Select

    The following table presents the various SQL statements related to reading records from tables and the corresponding MongoDB statements.

    SQL SELECT StatementsMongoDB find() StatementsReference
     
    SELECT *
FROM users

    db.users.find()
    		See find()for more information. 
    SELECT id, user_id, status
FROM users

    db.users.find(
    { },
    { user_id: 1, status: 1 }
)
    		See find()for more information. 
    SELECT user_id, status
FROM users

    db.users.find(
    { },
    { user_id: 1, status: 1, _id: 0 }
)
    		See find()for more information. 
    SELECT *
FROM users
WHERE status = "A"

    db.users.find(
    { status: "A" }
)
    		See find()for more information. 
    SELECT user_id, status
FROM users
WHERE status = "A"

    db.users.find(
    { status: "A" },
    { user_id: 1, status: 1, _id: 0 }
)
    		See find()for more information. 
    SELECT *
FROM users
WHERE status != "A"

    db.users.find(
    { status: { $ne: "A" } }
)
    		See find()and $ne for more information. 
    SELECT *
FROM users
WHERE status = "A"
AND age = 50

    db.users.find(
    { status: "A",
      age: 50 }
)
    		See find()and $and for more information. 
    SELECT *
FROM users
WHERE status = "A"
OR age = 50

    db.users.find(
    { $or: [ { status: "A" } ,
             { age: 50 } ] }
)
    		See find()and $or for more information. 
    SELECT *
FROM users
WHERE age > 25

    db.users.find(
    { age: { $gt: 25 } }
)
    		See find()and $gt for more information. 
    SELECT *
FROM users
WHERE age < 25

    db.users.find(
   { age: { $lt: 25 } }
)
    		See find()and $lt for more information. 
    SELECT *
FROM users
WHERE age > 25
AND   age <= 50

    db.users.find(
   { age: { $gt: 25, $lte: 50 } }
)
    		See find(),$gt, and$lte for more information. 
    SELECT *
FROM users
WHERE user_id like "%bc%"

    db.users.find(
   { user_id: /bc/ }
)
    		See find()and $regexfor more information. 
    SELECT *
FROM users
WHERE user_id like "bc%"

    db.users.find(
   { user_id: /^bc/ }
)
    		See find()and $regexfor more information. 
    SELECT *
FROM users
WHERE status = "A"
ORDER BY user_id ASC

    db.users.find( { status: "A" } ).sort( { user_id: 1 } )
    		See find()and sort()for more information. 
    SELECT *
FROM users
WHERE status = "A"
ORDER BY user_id DESC

    db.users.find( { status: "A" } ).sort( { user_id: -1 } )
    		See find()and sort()for more information. 
    SELECT COUNT(*)
FROM users

    db.users.count()

    or

    db.users.find().count()
    		See find()and count()for more information. 
    SELECT COUNT(user_id)
FROM users

    db.users.count( { user_id: { $exists: true } } )

    or

    db.users.find( { user_id: { $exists: true } } ).count()
    		See find(),count(), and $existsfor more information. 
    SELECT COUNT(*)
FROM users
WHERE age > 30

    db.users.count( { age: { $gt: 30 } } )

    or

    db.users.find( { age: { $gt: 30 } } ).count()
    		See find(),count(), and $gt for more information. 
    SELECT DISTINCT(status)
FROM users

    db.users.distinct( "status" )
    		See find()anddistinct()for more information. 
    SELECT *
FROM users
LIMIT 1

    db.users.findOne()

    or

    db.users.find().limit(1)
    		See find(),findOne(), and limit()for more information. 
    SELECT *
FROM users
LIMIT 5
SKIP 10

    db.users.find().limit(5).skip(10)
    		See find(),limit(), and skip()for more information. 
    EXPLAIN SELECT *
FROM users
WHERE status = "A"

    db.users.find( { status: "A" } ).explain()
    		See find()andexplain()for more information.

    Update Records

    The following table presents the various SQL statements related to updating existing records in tables and the corresponding MongoDB statements.

    SQL Update StatementsMongoDB update() StatementsReference
     
    UPDATE users
SET status = "C"
WHERE age > 25

    db.users.update(
   { age: { $gt: 25 } },
   { $set: { status: "C" } },
   { multi: true }
)
    		See update(), $gt, and $set for more information. 
    UPDATE users
SET age = age + 3
WHERE status = "A"

    db.users.update(
   { status: "A" } ,
   { $inc: { age: 3 } },
   { multi: true }
)
    		See update(), $inc, and $set for more information.

    Delete Records

    The following table presents the various SQL statements related to deleting records from tables and the corresponding MongoDB statements.

    SQL Delete StatementsMongoDB remove() StatementsReference
     
    DELETE FROM users
WHERE status = "D"

    db.users.remove( { status: "D" } )
    		See remove() for more information. 
    DELETE FROM users

    db.users.remove( )
    		See remove() for more information.
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  • 原文地址：https://www.cnblogs.com/sidesky/p/3235100.html
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