mysql - 如何在查询后合并字段，我知道 CONCAT，但不是这种方式

Question

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Answer 1

给你:

MySQL 使用 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 使用 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 使用 for xml path 和 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;