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 countFROM orders`	`db.orders.aggregate( [ { $group: { _id: null, count: { $sum: 1 } } }] )`	计算来自`orders`的所有记录
`SELECT SUM(price) AS totalFROM orders`	`db.orders.aggregate( [ { $group: { _id: null, total: { $sum: "$price" } } }] )`	`orders`中对`price`字段求和
`SELECT cust_id, SUM(price) AS totalFROM ordersGROUP 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 totalFROM ordersGROUP BY cust_idORDER 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 totalFROM ordersGROUP 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 ordersGROUP BY cust_idHAVING 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 totalFROM ordersGROUP BY cust_id, ord_dateHAVING 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 totalFROM ordersWHERE 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 totalFROM 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 } } }] )`	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 qtyFROM orders o, order_lineitem liWHERE li.order_id = o.idGROUP 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。

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译者：李冠飞

校对：

SQL 到聚合映射图表

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