sql - 为什么它说列定义不明确？

Question

select a.id_progdi, a.nama_progdi, avg(b.ipk)  
from tb_ipk b 
join tb_mahasiswa c on b.nim = c.nim 
join tb_progdi a on c.id_progdi = a.id_progdi  
group by id_progdi

Answer 1

你有多个id_progdi，所以它可能不知道在group by. 将其更改为group by a.id_progdi

Answer 2

在您的分组依据中，您应该添加表别名，因为您在多个表中具有相同的列名，并且数据库引擎需要知道您要引用哪个

    select a.id_progdi, a.nama_progdi, avg(b.ipk)  
    from tb_ipk b
    join  tb_mahasiswa c  on b.nim = c.nim 
    join tb_progdi a on c.id_progdi = a.id_progdi  
    group by a.id_progdi, a.nama_progdi

Answer 3

也许您在多个表中有 id_progdi 在您的组中使用表别名。