Question

我有两张桌子

Table A有三列：AID, first name, surname

Tabel B有四列：BID, AID, Address, TypeOFAddress

表A中的每个人在表B中各有四行。

Table_A
_AID_|_FIRST_|_LAST_
  1  | Leo   | White
  2  | Joe   | Black


Table_B
_BID_|_AID_|_ADDRESS_|_TYPE_
  10 |  1  |Street 1 |STREET
  11 |  1  |23490878 |ZIPCODE
  12 |  1  |Town 1   |CITY
  13 |  1  |Street 2 |STREET
  14 |  1  |83083099 |ZIPCODE
  15 |  1  |Town 2   |CITY

我想在一行中选择这些行，因此结果输出为

Result output
1  |Leo   |White |Street 1 |23490878 |Town
2  |Joe   |Black |Street 2 |83083099 |Town 2

我如何以一种很好的方式做到这一点？

Answer 1

首先，JOIN表。然后使用case表达式进行条件聚合：

select t1.AID, t1.FIRST, t1.LAST,
       max(case when t2.TypeOFAddress = 'STREET' then t2.Address end) STREET,
       max(case when t2.TypeOFAddress = 'ZIPCODE' then t2.Address end) ZIPCODE,
       max(case when t2.TypeOFAddress = 'CITY' then t2.Address end) CITY
from table1 t1
left join table2 t2 on t1.AID = t2.AID_
group by t1.AID, t1.FIRST, t1.LAST

Answer 2

如果您使用的是Microsoft SQL Server，则可以使用PIVOT

SELECT * FROM
    ( SELECT A.*, B.ADDRESS, B.TYPE 
      FROM Table_A A 
          INNER JOIN Table_B B ON A.AID = B.AID 
     ) SRC
    PIVOT (MAX([ADDRESS]) FOR TYPE IN ([STREET],[ZIPCODE],[CITY])) PVT

在一个结果行中选择两个表连接

2 个答案: