Create temporary columns in mysql

Create temporary columns in mysql
When I write an SQL statement today, the following error occurs: SELECT COUNT (s_dayreport. *) FROM s_dayreport INNER JOIN s _
Subuser ON s_dayreport.userId = s_subuser.userId WHERE s_subuser.mgrId = 63 error message: www.2cto.com says My SQL error, modify as follows: SELECT COUNT (*) FROM s_dayreport where exists (select 1 from
S_subuser where s_subuser.mgrId = 63 and s_dayreport.userId = s_subuser.userId)
Exists is equivalent to the sum of a condition. select 1 is used to create a temporary column. Column name 1