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(译文)SQL与Mongodb聚合之前的对应关系
本文翻译自:https://docs.mongodb.com/manual/reference/sql-aggregation-comparison/
由于本人也在学习Mongodb,项目中用到聚合,看到文档这篇不错就翻译一下(仅供参考)
SQL中的聚合函数和Mongodb中的管道相互对应的关系:
WHERE $match GROUP BY $group HAVING $match SELECT $project ORDER BY $sort LIMIT $limit SUM() $sum COUNT() $sum join $lookup
例子:
先创建文档,填充数据
/* 0 */
{
"_id" : ObjectId("5812b447311bb4272016496a"),
"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
}]
}
/* 1 */
{
"_id" : ObjectId("58131494311bb418b058fcba"),
"cust_id" : "a",
"ord_date" : ISODate("2012-11-02T17:04:11.102Z"),
"status" : "B",
"price" : 70,
"items" : [{
"sku" : "xxx",
"qty" : 25,
"price" : 1
}, {
"sku" : "yyy",
"qty" : 25,
"price" : 1
}]
}
/* 2 */
{
"_id" : ObjectId("581314b6311bb418b058fcbb"),
"cust_id" : "ab",
"ord_date" : ISODate("2012-11-02T17:04:11.102Z"),
"status" : "E",
"price" : 60,
"items" : [{
"sku" : "xxx",
"qty" : 55,
"price" : 1
}, {
"sku" : "yyy",
"qty" : 25,
"price" : 1
}]
}
例1:
SQL：
SELECT COUNT(*) AS count FROM orders
Mongodb：
db.orders.aggregate([
{
$group:{
_id:null,
count:{$sum:1}
}
}
])
例2：
SQL：
SELECT SUM(price) AS total FROM orders
Mongodb：
db.orders.aggregate(
[
{
$group:
{
_id:null,
total:{$sum:"$price"}
}
}
])
例3：
SQL:
SELECT cust_id,SUM(price) AS total FROM orders GROUP BY cust_id
Mongodb:
db.orders.aggregate([
{
$group:
{
_id:"$cust_id",
total:
{
$sum:"$price"
}
}
},
{
$sort:
{
total:1
}
}
])
例4：
SQL：
SELECT cust_id, ord_date,SUM(price) AS total FROM orders GROUP BY cust_id, ord_date
Mongodb：
db.orders.aggregate([
{
$group:
{
_id:
{
cust_id:"$cust_id",
ord_date:
{
month:{$month:"$ord_date"},
day:{$dayOfMonth:"$ord_date"},
year:{$year:"$ord_date"}
}
},
total:{$sum:"$price"}
}
}
])
(译文)SQL与Mongodb聚合之前的对应关系
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