How to write a select query which will return records if condition in where clause satisfies all the values

Question

I have a requirement where I need to write a select query which will return records if condition in where clause satisfies all the values.

for eg:

I have employee table, with three reocords, lets assume Name is the one column( having three records 'A', 'B', 'C')

select * from emp where Name in ('A', 'B', 'D') --- it should not return any values as D value is not there, please suggest me the select query

Answer 1

using IN will return rows where any of the conditions are met, as if you used OR.

select * from emp where Name in ('A', 'B', 'D')

is equal to:

select * from emp where Name = 'A' OR Name = 'B' OR Name = 'D'

If your emp-table only has 'A', 'B' and 'C', the result should be: 'A' and 'B' rows.

If you want result to show none records or all records, that is not easy with a single SQL select, you will have to use Oracle/PLSQL if-then-else, something like this:

IF (select count(*) from emp where name in ('A', 'B', 'C')) = 3 THEN
    select * from emp where name in ('A', 'B', 'C')
ELSE
    select * from emp where name is null
END IF;

The else-part here is added just to return an empty dataset, assuming none records has NULL value in the name column.