将两个表，多行连接成一行不同的列

Question

我有两张桌子，

write.csv(x, file = "c:\\myname\\yourfile.csv", row.names = FALSE)

输出应该是，

USER

USER_ID | USER_NAME
--------------------
659    |  John  
660    |  Andrew 
661    |  Bianca
--------------------


USER_ADDRESS

USER_ID |TYPE |    ADDRESS
------------------------------
659     | HOME |    New York
659     | WORK |    New Jersey
660     | HOME |    San Francisco
660     | WORK |    Fremont
------------------------------

如何在选择查询中获得上述输出？提前谢谢！

Answer 1

试试这个：

SELECT u.*, uah.address as home_address, uaw.address as work_address
FROM users u
LEFT OUTER JOIN user_address uah
    ON u.user_id = uah.user_id
    AND uah.type = 'HOME'
LEFT OUTER JOIN user_address uaw
    ON u.user_id = uaw.user_id
    AND uaw.type = 'WORK'