本文介绍了MongoDB选择并连接字段的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有一个非常基本的问题:
SELECT name, surname CONCAT(name, surname) AS name_surname from users;
如何将该SQL
转换为MongoDB
查询?
在搜索过程中,由于concat
,我已经决定使用聚合框架是可能的,但是我收到的只是concat(name, surname)
中的projection
,而不是name
,surname
和concat(name, surname)
. /p>
我最后得到的是这个查询:
db.inroamers.find().forEach(
function(o) {
print(o.LAC + '-' + o.CELL + ' ' + o.CHARGE + ' ' + o.WEEK);
})
但是它不能给我正确的json
数组.
有什么建议吗?
解决方案
使用以下聚合操作:
db.collection.aggregate([
{$project:{"name_surname":{$concat:["$name","-","$surname"]},"name":1,"surname":1}}
])
I have a very basic question:
SELECT name, surname CONCAT(name, surname) AS name_surname from users;
How can I convert this SQL
to MongoDB
query?
During my search, I have decided that it is possible with aggregate framework due to concat
, but what I received is only projection
of concat(name, surname)
not name
, surname
and concat(name, surname)
.
Final thing I got is this query:
db.inroamers.find().forEach(
function(o) {
print(o.LAC + '-' + o.CELL + ' ' + o.CHARGE + ' ' + o.WEEK);
})
but it does not give me proper json
array.
Any suggestions?
解决方案
Use the aggregation operations as below:
db.collection.aggregate([
{$project:{"name_surname":{$concat:["$name","-","$surname"]},"name":1,"surname":1}}
])
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