How to Merge fields after query, i know CONCAT, but not this way

Question

I know the way to merge field in

• MySQL: CONCAT( )
• Oracle: CONCAT( ), ||
• SQL Server: `+

but... I wanna merge AFTER query, is it possible?

Answer 1

Here you go:

MySQL using group_concat:

select a.name,
    a.opcode,
    group_concat(month order by b.pk separator ', ') as months
from tablea a
join tableb b on a.opcode = b.opcode
group by a.name, a.opcode;

Oracle using listagg:

select a.name,
    a.opcode,
    listagg(month,', ') within group (order by b.pk) as months
from tablea a
join tableb b on a.opcode = b.opcode
group by a.name, a.opcode;

SQL Server using for xml path and stuff:

select a.*,
    stuff((
        select ', ' + month from tableb b
        where a.opcode = b.opcode
        order by pk 
        for xml path(''), type
        ).value('(./text())[1]', 'varchar(max)')
    , 1, 2, '') as months
from tablea a;