从一列中选择电话号码成多列sql

Question

我有一个称为phone的表，我需要在六个单独的列中返回前三个电话号码和每种c_no的三种类型，然后再加入contacts表。 电话桌的布局是这样的，

p_no,c_no, phone, p_type

我想要的结果集是

c_no, First_Phone, First_Phone_Type, Second_Phone, Second_Phone_Type, Third_Phone, Third_Phone_Type

我尝试了以下操作，但是当我通过c_no添加组时，第二列或第三列中没有显示任何内容

select  c_no,
        (case when cp_sort = 1 and cp_status = 1 then phone end) as Phone_1,
        (case when cp_sort = 2 and cp_status = 1 then phone end) as Phone_2,
        (case when cp_sort = 3 and cp_status = 1 then phone end) as Phone_3
 from   phones cp  
 group by
         c_no

提前非常感谢你们提供的所有帮助！

Answer 1

您可以尝试：

select distinct c_no, 
  (select phone from phones p1 where p0.c_no = p1.c_no and cp_sort = 1) Phone_1,
  (select phone from phones p2 where p0.c_no = p2.c_no and cp_sort = 2) Phone_2,
  (select phone from phones p3 where p0.c_no = p3.c_no and cp_sort = 3) Phone_3
from phones p0;

可能需要一些优化才能在大量数据上正常工作。