我有一个 MYSQL 表 - 为了简化它 - 三列：名称、地址和主要住所。
可以有重复名称的行。我想做一个选择语句，它将返回一个人的姓名和地址。如果他们在表中两次，这意味着他们有两个地址。但是，如果其中一个是“主要住所”，我希望它只返回主要住所。否则，它应该返回两个地址。谢谢！
桌子：
Name | Address | Primary Residence
John Smith | 123 Main Str | Yes
John Smith | 456 June Str |
Mike Dore | 893 West St |
Jake John | 999 East St |
Jake John | 145 South St |
回报：
Name | Address
John Smith | 123 Main Str
Mike Dore | 893 West St
Jake John | 999 East St
Jake John | 145 South St
这是一种方法...
CREATE TABLE addresses
(Name VARCHAR(20) NOT NULL
,Address VARCHAR(20) NOT NULL
,is_primary TINYINT NULL
,PRIMARY KEY (name,address)
);
INSERT INTO addresses VALUES
('John Smith','123 Main Str',1),
('John Smith','456 June Str',NULL),
('Mike Dore','893 West St',NULL),
('Jake John','999 East St',NULL),
('Jake John','145 South St',NULL);
SELECT * FROM addresses;
+------------+--------------+------------+
| Name | Address | is_primary |
+------------+--------------+------------+
| Jake John | 145 South St | NULL |
| Jake John | 999 East St | NULL |
| John Smith | 123 Main Str | 1 |
| John Smith | 456 June Str | NULL |
| Mike Dore | 893 West St | NULL |
+------------+--------------+------------+
SELECT DISTINCT x.name
, COALESCE(y.address,x.address) address
FROM addresses x
LEFT
JOIN addresses y
ON y.name = x.name
AND y.is_primary = 1;
+------------+--------------+
| name | address |
+------------+--------------+
| Jake John | 145 South St |
| Jake John | 999 East St |
| John Smith | 123 Main Str |
| Mike Dore | 893 West St |
+------------+--------------+
它可以通过子查询来完成。
select * from TBL where NAME not in (select NAME from TBL where residence='PRI')
union
select * from TBL where residence='PRI';
编辑：问题更新后：
select * from TBL where NAME not in (select NAME from TBL where residence='yes')
union
select * from TBL where residence='yes'