mongoDB与sql聚合操作对应图
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
joinNo direct corresponding operator; however, the $unwindoperator allows for somewhat similar functionality, but with fields embedded within the document.
实例：
SQL ExampleMongoDB ExampleDescription
SELECT COUNT(*) AS countFROM orders
db.orders.aggregate( [ { $group: { _id: null, count: { $sum: 1 } } }] )
Count all records fromorders
SELECT SUM(price) AS totalFROM orders
db.orders.aggregate( [ { $group: { _id: null, total: { $sum: "$price" } } }] )
Sum theprice field from orders，这个非常有用，看官方说明，说_ID是必须，但没想到可以为NULL,
SELECT cust_id, SUM(price) AStotalFROM ordersGROUP BY cust_id
db.orders.aggregate( [ { $group: { _id: "$cust_id", total: { $sum: "$price" } } }] )
For each uniquecust_id, sum the pricefield.
SELECT cust_id, SUM(price) AStotalFROM ordersGROUP BYcust_idORDER BY total
db.orders.aggregate( [ { $group: { _id: "$cust_id", total: { $sum: "$price" } } }, { $sort: { total: 1 } }] )
For each uniquecust_id, sum the pricefield, results sorted by sum.
SELECT cust_id, ord_date, SUM(price) AS totalFROM ordersGROUPBY 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_dategrouping, sum the pricefield.
SELECT cust_id, count(*)FROMordersGROUP BY cust_idHAVING count(*)> 1
db.orders.aggregate( [ { $group: { _id: "$cust_id", count: { $sum: 1 } } }, { $match: { count: { $gt: 1 } } }] )
For cust_idwith multiple records, return thecust_id and the corresponding record count.
SELECT cust_id, ord_date, SUM(price) AS totalFROM ordersGROUPBY cust_id, ord_dateHAVING total > 250
db.orders.aggregate( [ { $group: { _id: { cust_id: "$cust_id", ord_date: "$ord_date" }, total: { $sum: "$price" } } }, { $match: { total: { $gt: 250 } } }] )
For each uniquecust_id,ord_dategrouping, sum the pricefield and return only where the sum is greater than 250.
SELECT cust_id, SUM(price) astotalFROM ordersWHERE status ='A'GROUP BY cust_id
db.orders.aggregate( [ { $match: { status: 'A' } }, { $group: { _id: "$cust_id", total: { $sum: "$price" } } }] )
For each uniquecust_id with status A, sum the pricefield.
SELECT cust_id, SUM(price) astotalFROM ordersWHERE status ='A'GROUP BY cust_idHAVING total > 250
db.orders.aggregate( [ { $match: { status: 'A' } }, { $group: { _id: "$cust_id", total: { $sum: "$price" } } }, { $match: { total: { $gt: 250 } } }] )
For each uniquecust_id with status A, sum the pricefield and return only where the sum is greater than 250.
SELECT cust_id, SUM(li.qty) asqtyFROM orders o, order_lineitem liWHERE li.order_id = o.idGROUP BYcust_id
db.orders.aggregate( [ { $unwind: "$items" }, { $group: { _id: "$cust_id", qty: { $sum: "$items.qty" } } }] )
For each uniquecust_id, sum the corresponding line item qtyfields associated with the orders.
SELECT COUNT(*)FROM (SELECT cust_id, ord_date FROM orders GROUP BYcust_id, ord_date) as DerivedTable
db.orders.aggregate( [ { $group: { _id: { cust_id: "$cust_id", ord_date: "$ord_date" } } }, { $group: { _id: null, count: { $sum: 1 } } }] )
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