SQL 到聚合映射图表

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SQL 到聚合映射图表
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​例子​
​聚合管道允许 MongoDB 提供与 SQL 中许多 common 数据聚合操作相对应的本机聚合功能。
以下 table 概述了 common SQL 聚合术语，函数和概念以及相应的 MongoDB 聚合运算符：
SQL 术语，函数和概念
Mongo聚合命令
WHERE
​$match​
GROUP BY
​$group​
HAVING
​$match​
SELECT
​$project​
ORDER BY
​$sort​
LIMIT
​$limit​
SUM()
​$sum​
COUNT()
​$sum $sortByCount​
join
​$lookup​
SELECT INTO NEW_TABLE
​$out​
MERGE INTO TABLE
​$merge （从MongoDB 4.2开始可用）
有关所有聚合管道和表达式 operators 的列表，请参阅聚合管道快速参考。
也可以看看
SQL 到 MongoDB 映射图表](SQL-to-Aggregation-Mapping-Chart.md)
例子
以下 table 提供了 SQL 聚合 statements 和相应的 MongoDB statements 的快速 reference。 table 中的示例假定以下条件：
SQL 示例假设两个表orders和order_lineitem由order_lineitem.order_id和orders.id列连接。
MongoDB 示例假设一个集合orders包含以下原型的文档：
{
  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 } ]
}
SQL语句
MongoDB语句
描述
SELECT COUNT(*) AS count FROM orders
db.orders.aggregate( [ { $group: { _id: null, count: { $sum: 1 } } } ] )
计算来自orders的所有记录
SELECT SUM(price) AS total FROM orders
db.orders.aggregate( [ { $group: { _id: null, total: { $sum: "$price" } } } ] )
orders中对price字段求和
SELECT cust_id, SUM(price) AS total FROM orders GROUP BY cust_id
db.orders.aggregate( [ { $group: { _id: "$cust_id", total: { $sum: "$price" } } } ] )
对于每个唯一cust_id，对price字段进行求和。
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 } } ] )
对于每个唯一cust_id，求和price字段，结果按总和排序。
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: { $dateToString: { format: "%Y-%m-%d", date: "$ord_date" }} }, total: { $sum: "$price" } } } ] )
对于每个唯一的cust_id，通过ord_date分组，将price字段相加。排除 data 的 time 部分。
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 } } } ] )
对于具有多个记录的cust_id，返回cust_id和相应的 record 计数。
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: { $dateToString: { format: "%Y-%m-%d", date: "$ord_date" }} }, total: { $sum: "$price" } } }, { $match: { total: { $gt: 250 } } } ] )
对于每个唯一的cust_id，通过ord_date分组，仅在总和大于 250 的情况下对price字段和 return 求和。排除 date 的 time 部分
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" } } } ] )
对于状态为A的每个唯一cust_id，请对price字段求和。
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 } } } ] )
对于状态为A的每个唯一cust_id，仅对总和大于 250 的price字段和 return 求和。
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" } } } ] )
对于每个唯一cust_id，将与订单关联的相应 line item qty字段相加。
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: { $dateToString: { format: "%Y-%m-%d", date: "$ord_date" }} } } }, { $group: { _id: null, count: { $sum: 1 } } } ] )
计算不同的cust_id，ord_date分组的数量。排除 date 的 time 部分。
也可以看看
​SQL 到 MongoDB 映射图表​
​聚合管道快速参考​
​db.collection.aggregate()​
译者：李冠飞
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