SQL to Aggregation Framework Mapping Chart¶
The aggregation framework allows MongoDB to provide native aggregation capabilities that corresponds to many common data aggregation operations in SQL. If you’re new to MongoDB you might want to consider the Frequently Asked Questions section for a selection of common questions.
The following table provides an overview of common SQL aggregation terms, functions, and concepts and the corresponding MongoDBaggregation operators:
| SQL Terms, Functions, and Concepts | MongoDB Aggregation Operators |
|---|---|
| WHERE | $match |
| GROUP BY | $group |
| HAVING | $match |
| SELECT | $project |
| ORDER BY | $sort |
| LIMIT | $limit |
| SUM() | $sum |
| COUNT() | $sum |
| join | No direct corresponding operator;however, the $unwind operator allows for somewhat similar functionality, but with fields embedded within the document. |
Examples¶
The following table presents a quick reference of SQL aggregation statements and the corresponding MongoDB statements. The examples in the table assume the following conditions:
-
The SQL examples assume two tables, orders andorder_lineitem that join by the order_lineitem.order_id and the orders.id columns.
-
The MongoDB examples assume one collection orders that contain documents of the following prototype:
{ cust_id: "abc123", ord_date: ISODate("2012-11-02T17:04:11.102Z"), status: 'A', price: 50, items: [ { sku: "xxx", qty: 25, price: 1 }, { sku: "yyy", qty: 25, price: 1 } ] }
-
The MongoDB statements prefix the names of the fields from thedocuments in the collection orders with a$ character when they appear as operands to the aggregation operations.
| SQL Example | MongoDB Example | Description |
|---|---|---|
SELECT COUNT(*) AS count
FROM orders
|
db.orders.aggregate( [
{ $group: { _id: null,
count: { $sum: 1 } } }
] )
|
Count all records from orders |
SELECT SUM(price) AS total
FROM orders
|
db.orders.aggregate( [
{ $group: { _id: null,
total: { $sum: "$price" } } }
] )
|
Sum the price field from orders |
SELECT cust_id,
SUM(price) AS total
FROM orders
GROUP BY cust_id
|
db.orders.aggregate( [
{ $group: { _id: "$cust_id",
total: { $sum: "$price" } } }
] )
|
For each unique cust_id, sum the price field. |
SELECT cust_id,
SUM(price) AS total
FROM orders
GROUP BY cust_id
ORDER BY total
|
db.orders.aggregate( [
{ $group: { _id: "$cust_id",
total: { $sum: "$price" } } },
{ $sort: { total: 1 } }
] )
|
For each unique cust_id, sum the price field, results sorted by sum. |
SELECT cust_id,
ord_date,
SUM(price) AS total
FROM orders
GROUP BY cust_id, ord_date
|
db.orders.aggregate( [
{ $group: { _id: { cust_id: "$cust_id",
ord_date: "$ord_date" },
total: { $sum: "$price" } } }
] )
|
For each uniquecust_id, ord_date grouping, sum the price field. |
SELECT cust_id, count(*)
FROM orders
GROUP BY cust_id
HAVING count(*) > 1
|
db.orders.aggregate( [
{ $group: { _id: "$cust_id",
count: { $sum: 1 } } },
{ $match: { count: { $gt: 1 } } }
] )
|
For cust_id with multiple records, return the cust_id and the corresponding record count. |
SELECT cust_id,
ord_date,
SUM(price) AS total
FROM orders
GROUP BY cust_id, ord_date
HAVING total > 250
|
db.orders.aggregate( [
{ $group: { _id: { cust_id: "$cust_id",
ord_date: "$ord_date" },
total: { $sum: "$price" } } },
{ $match: { total: { $gt: 250 } } }
] )
|
For each unique cust_id, ord_dategrouping, sum the price field and return only where the sum is greater than 250. |
SELECT cust_id,
SUM(price) as total
FROM orders
WHERE status = 'A'
GROUP BY cust_id
|
db.orders.aggregate( [
{ $match: { status: 'A' } },
{ $group: { _id: "$cust_id",
total: { $sum: "$price" } } }
] )
|
For each unique cust_idwith status A, sum the price field. |
SELECT cust_id,
SUM(price) as total
FROM orders
WHERE status = 'A'
GROUP BY cust_id
HAVING total > 250
|
db.orders.aggregate( [
{ $match: { status: 'A' } },
{ $group: { _id: "$cust_id",
total: { $sum: "$price" } } },
{ $match: { total: { $gt: 250 } } }
] )
|
For each unique cust_idwith status A, sum the price field and return only where the sum is greater than 250. |
SELECT cust_id,
SUM(li.qty) as qty
FROM orders o,
order_lineitem li
WHERE li.order_id = o.id
GROUP BY cust_id
|
db.orders.aggregate( [
{ $unwind: "$items" },
{ $group: { _id: "$cust_id",
qty: { $sum: "$items.qty" } } }
] )
|
For each unique cust_id, sum the corresponding line item qty fields associated with the orders. |
SELECT COUNT(*)
FROM (SELECT cust_id, ord_date
FROM orders
GROUP BY cust_id, ord_date) as DerivedTable
|
db.orders.aggregate( [
{ $group: { _id: { cust_id: "$cust_id",
ord_date: "$ord_date" } } },
{ $group: { _id: null, count: { $sum: 1 } } }
] )
|