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SQL to MongoDB Mapping Chart

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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.

Terminology and Concepts

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

SQL Terms/Concepts MongoDB 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 pipeline

See the SQL to Aggregation Mapping Chart.

Executables

The following table presents some database executables and the corresponding MongoDB executables. This table is not meant to be exhaustive.

  MongoDB MySQL Oracle Informix DB2
Database Server mongod mysqld oracle IDS DB2 Server
Database Client mongo mysql sqlplus DB-Access DB2 Client

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 Statements MongoDB Schema Statements 
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")

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 }
)

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 }
)

CREATE INDEX idx_user_id_asc
ON users(user_id)

db.users.createIndex( { user_id: 1 } )

CREATE INDEX
       idx_user_id_asc_age_desc
ON users(user_id, age DESC)

db.users.createIndex( { user_id: 1, age: -1 } )

DROP TABLE users

db.users.drop()

For more information, see db.collection.insert(), db.createCollection(), db.collection.update(), $set, $unset, db.collection.createIndex(), indexes, db.collection.drop(), and Data Modeling Concepts.

Insert

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

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

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

For more information, see db.collection.insert().

Select

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

SQL SELECT Statements MongoDB find() Statements 
SELECT *
FROM users

db.users.find()

SELECT id,
       user_id,
       status
FROM users

db.users.find(
    { },
    { user_id: 1, status: 1 }
)

SELECT user_id, status
FROM users

db.users.find(
    { },
    { user_id: 1, status: 1, _id: 0 }
)

SELECT *
FROM users
WHERE status = "A"

db.users.find(
    { status: "A" }
)

SELECT user_id, status
FROM users
WHERE status = "A"

db.users.find(
    { status: "A" },
    { user_id: 1, status: 1, _id: 0 }
)

SELECT *
FROM users
WHERE status != "A"

db.users.find(
    { status: { $ne: "A" } }
)

SELECT *
FROM users
WHERE status = "A"
AND age = 50

db.users.find(
    { status: "A",
      age: 50 }
)

SELECT *
FROM users
WHERE status = "A"
OR age = 50

db.users.find(
    { $or: [ { status: "A" } ,
             { age: 50 } ] }
)

SELECT *
FROM users
WHERE age > 25

db.users.find(
    { age: { $gt: 25 } }
)

SELECT *
FROM users
WHERE age < 25

db.users.find(
   { age: { $lt: 25 } }
)

SELECT *
FROM users
WHERE age > 25
AND   age <= 50

db.users.find(
   { age: { $gt: 25, $lte: 50 } }
)

SELECT *
FROM users
WHERE user_id like "%bc%"

db.users.find( { user_id: /bc/ } )

SELECT *
FROM users
WHERE user_id like "bc%"

db.users.find( { user_id: /^bc/ } )

SELECT *
FROM users
WHERE status = "A"
ORDER BY user_id ASC

db.users.find( { status: "A" } ).sort( { user_id: 1 } )

SELECT *
FROM users
WHERE status = "A"
ORDER BY user_id DESC

db.users.find( { status: "A" } ).sort( { user_id: -1 } )

SELECT COUNT(*)
FROM users

db.users.count()

or

db.users.find().count()

SELECT COUNT(user_id)
FROM users

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

or

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

SELECT COUNT(*)
FROM users
WHERE age > 30

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

or

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

SELECT DISTINCT(status)
FROM users

db.users.distinct( "status" )

SELECT *
FROM users
LIMIT 1

db.users.findOne()

or

db.users.find().limit(1)

SELECT *
FROM users
LIMIT 5
SKIP 10

db.users.find().limit(5).skip(10)

EXPLAIN SELECT *
FROM users
WHERE status = "A"

db.users.find( { status: "A" } ).explain()

For more information, see db.collection.find(), db.collection.distinct(), db.collection.findOne(), $ne $and, $or, $gt, $lt, $exists, $lte, $regex, limit(), skip(), explain(), sort(), and count().

Update Records

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

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

db.users.update(
   { age: { $gt: 25 } },
   { $set: { status: "C" } },
   { multi: true }
)

UPDATE users
SET age = age + 3
WHERE status = "A"

db.users.update(
   { status: "A" } ,
   { $inc: { age: 3 } },
   { multi: true }
)

For more information, see db.collection.update(), $set, $inc, and $gt.

Delete Records

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

SQL Delete Statements MongoDB remove() Statements 
DELETE FROM users
WHERE status = "D"

db.users.remove( { status: "D" } )

DELETE FROM users

db.users.remove({})

For more information, see db.collection.remove().

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