sql 連接同一張表的2行

Question

我有下表：

Name   Type     Value
---------------------
mike   phone    123    
mike   address  nyc    
bob    address  nj    
bob    phone    333

我想要這樣的結果：

name  value  value
-------------------
mike  nyc    123
bob   nj     333

我該怎么做？

Answer 1

它被稱為自聯接。 訣竅是使用別名。

select 
    address.name,
    address.value as address,
    phone.value as phone
from
    yourtable as address left join
    yourtable as phone on address.name = phone.name
where address.type = 'address' and
      (phone.type is null or phone.type = 'phone')

該查詢假定每個姓名都有一個地址，但電話號碼是可選的。

Answer 2

像這樣的東西：

SELECT a.name AS name, phone, address
    FROM (SELECT name, value AS phone FROM mytable WHERE type = "phone") AS a
    JOIN (SELECT name, value AS address FROM mytable WHERE type = "address") AS b
    ON(a.name = b.name);