如何在我的SQL中连接两个查询

Question

 select concat_ws((
select count(*) from feed_back where schedule_id=1),'/',(select count(*) from event_schedule_mapping where event_schedule_id=1))
as total

我从两个查询中得到了数据，但是当我尝试使用concat concat_ws时，它给我blobdata为空白请告诉我哪里出错了请建议。

Answer 1

为什么concat_ws()而不是concat()？

SELECT CONCAT( (First Select),
                '/'
               (Second Select)) as total

Answer 2

首先使用分隔符尝试此操作：

    SELECT CONCAT_WS('/', 
        (select count(*) from feed_back where schedule_id=1), 
        (select count(*) from event_schedule_mapping where event_schedule_id=1))

String Functions - MySQL CONCAT_WS

Answer 3

尝试这样

＆＃13;

＆＃13;

SELECT sum(a+b) as total FROM (SELECT count(*) as a from feed_back where schedule_id=1) as x, (SELECT count(*) as b FROM event_schedule_mapping where event_schedule_id=1) as y

＆＃13;

＆＃13;

＆＃13;