where 子句中的表列值

Question

I have two table

Employee

EmployeeId	Name	Job
123	David	yes
124	Timothy	yes
125	Maxi	No
126	Abie

EmployeeResidence

Id	EmployeeId	EmployeeSpclField	EmployeeSpclValue
1	123	Married	yes
2	123	Nationality	MEX
3	123	Job	Fitter
4	124	Married	yes
5	124	Nationality	ARG
6	125	Job	Driver

I need a Sql query that returns 1 or 0 based on the Bind value Employee id and I need the following conditions to be validated

1. job should not be null 2)Nationality should not be null and he should belong to MEX

So how can i do that ? I am building something like this

select 1 from Employee emp ,EmployeeResidence er 
where 
employeeid=:empid and emp.job is not null and 

I am struggling to include EmployeeSpclField column value to check if it is not null and belongs to MEX

Answer 1

I might avoid a join and instead use exists logic here:

SELECT e.*
FROM Employee e
WHERE Job IS NOT NULL AND
      EXISTS (SELECT 1 FROM EmployeeResidence er
              WHERE er.EmployeeId = e.EmployeeId AND
                    er.EmployeeSpclField = 'Nationality' AND
                    er.EmployeeSpclValue = 'MEX');

Answer 2

Select a 0/1 flag

select case when exists (
    select 1 
    from Employee emp 
    join EmployeeResidence er 
      on emp.employeeid = er.employeeid and er.EmployeeSpclField = 'Nationality' and er.EmployeeSpclValue = 'MEX'
    where emp.employeeid=:empid and emp.job is not null ) then 1
   else 0 end flag 
from dual;

Answer 3

Try this:

Select
e.EmployeeID,
case when er.EmployeeID is null then 0 else 1 end as return_val
from
Employee e
left outer join
(select EmployeeId,
 max(case when EmployeeSpclField='Married' then EmployeeSpclValue else NULL end) as married,
 max(case when EmployeeSpclField='Nationality' then EmployeeSpclValue else NULL end) as Nationality,
 max(case when EmployeeSpclField='Job' then EmployeeSpclValue else NULL end) as Job
from 
 EmployeeResidence
group by
EmployeeId) er
on e.EmployeeId=er.EmployeeId
and e.Job is not null 
and (er.Nationality is not null and er.Nationality ='MEX')

Answer 4

One option might be using conditional aggregation in order to count desired conditions

SELECT SIGN(NVL(SUM(CASE WHEN er.EmployeeSpclField = 'Nationality' 
                          AND er.EmployeeSpclValue = 'MEX' 
                          AND e.Job IS NOT NULL THEN 1 ELSE 0 END),0)) 
    AS Result
  FROM Employee e
  JOIN EmployeeResidence er
    ON er.EmployeeId = e.EmployeeId
 WHERE e.EmployeeId = :empid

where SIGN() function is used considering the possibility to have duplicate records for Nationality value for EmployeeSpclField column per any of EmployeeId column's value.

Demo