mongodb查询，如何实现字段的别名？ 和sql中select name as new_name from table;那样的效果

Posted 2023-04-14

参考技术A mongodb里可以实现别名查询，通过聚合管道可以实现最后的聚合结果
db.sales.aggregate($project:myid:"$_id",日期:"$date")
上面的日期即为别名 参考技术B mongodb实现不了查询后，以别名命名新的查询结果的字段！

查询只能按照字段的名称进行查询，并且查询的属性名必须大小写匹配。本回答被提问者采纳

sql 中如何用别名作为查询条件

两个sql语句是用union连接的，例如:
select a.id as 'id',a.membername as 'name' b.suppliername as 'companyname' from member a
inner join supplier b on a.supplierid=b.supplierid where company like'%某某%'
union
select a.id as 'id',a.membername as 'name' b.customername as 'companyname' from member a
inner join customer b on a.customerid=b.customerid where companyname like '%某某%'
像这样的查询怎么用别名作为查询条件啊

SQL Server 2005/2008
Oracle 10/11

可以用 CTE， 来 “曲线”的实现这个要求.

例如：

1> with myCTE AS (
2> SELECT 1+2+3+4 AS 别名 UNION ALL
3> SELECT 2+3+4+5 AS 别名
4> )
5> SELECT * FROM myCTE WHERE 别名 = 10
6> go
别名
-----------
10

(1 行受影响) 参考技术A select * from (select a.id as 'id',a.membername as 'name' b.suppliername as 'companyname' from member a
inner join supplier b on a.supplierid=b.supplierid
union
select a.id as 'id',a.membername as 'name' b.customername as 'companyname' from member a
inner join customer b on a.customerid=b.customerid) a where companyname like '%某某%'本回答被提问者采纳