SQL to Aggregation Framework Mapping Chart

 

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 } } } ] )

转载于:https://www.cnblogs.com/fx2008/archive/2013/03/28/2986592.html