我正在尝试执行以下查询:
INSERT INTO table_listnames (name, address, tele)
VALUES ('Rupert', 'Somewhere', '022')
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name='value'
);
但是这会返回一个错误。基本上我不想插入一个记录,如果记录的“名称”字段已经存在于另一个记录-如何检查新名称是否唯一?
我正在尝试执行以下查询:
INSERT INTO table_listnames (name, address, tele)
VALUES ('Rupert', 'Somewhere', '022')
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name='value'
);
但是这会返回一个错误。基本上我不想插入一个记录,如果记录的“名称”字段已经存在于另一个记录-如何检查新名称是否唯一?
当前回答
这个查询可以在PHP代码中使用。
我在这个表中有一个ID列,所以我需要检查除了这个ID列之外的所有列的复制:
#need to change values
SET @goodsType = 1, @sybType=5, @deviceId = asdf12345SDFasdf2345;
INSERT INTO `devices` (`goodsTypeId`, `goodsId`, `deviceId`) #need to change tablename and columnsnames
SELECT * FROM (SELECT @goodsType, @sybType, @deviceId) AS tmp
WHERE NOT EXISTS (
SELECT 'goodsTypeId' FROM `devices` #need to change tablename and columns names
WHERE `goodsTypeId` = @goodsType
AND `goodsId` = @sybType
AND `deviceId` = @deviceId
) LIMIT 1;
现在只有在SET字符串中配置的值不存在的情况下才会添加新项
其他回答
我并不是建议你这样做,因为Piskvor和其他人建议的UNIQUE索引是一个更好的方法,但你实际上可以做你正在尝试的事情:
CREATE TABLE `table_listnames` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(255) NOT NULL,
`address` varchar(255) NOT NULL,
`tele` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB;
插入一个记录:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'Rupert', 'Somewhere', '022') AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'Rupert'
) LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
SELECT * FROM `table_listnames`;
+----+--------+-----------+------+
| id | name | address | tele |
+----+--------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
+----+--------+-----------+------+
尝试再次插入相同的记录:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'Rupert', 'Somewhere', '022') AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'Rupert'
) LIMIT 1;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
+----+--------+-----------+------+
| id | name | address | tele |
+----+--------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
+----+--------+-----------+------+
插入一条不同的记录:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'John', 'Doe', '022') AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'John'
) LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
SELECT * FROM `table_listnames`;
+----+--------+-----------+------+
| id | name | address | tele |
+----+--------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
| 2 | John | Doe | 022 |
+----+--------+-----------+------+
等等……
更新:
为了防止#1060 -重复列名错误,如果两个值可能相等,你必须命名内部SELECT的列:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'Unknown' AS name, 'Unknown' AS address, '022' AS tele) AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'Rupert'
) LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
SELECT * FROM `table_listnames`;
+----+---------+-----------+------+
| id | name | address | tele |
+----+---------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
| 2 | John | Doe | 022 |
| 3 | Unknown | Unknown | 022 |
+----+---------+-----------+------+
如果真的无法在表上获得唯一索引,您可以尝试…
INSERT INTO table_listnames (name, address, tele)
SELECT 'Rupert', 'Somewhere', '022'
FROM some_other_table
WHERE NOT EXISTS (SELECT name
FROM table_listnames
WHERE name='Rupert')
LIMIT 1;
这个查询很有效:
INSERT INTO `user` ( `username` , `password` )
SELECT * FROM (SELECT 'ersks', md5( 'Nepal' )) AS tmp
WHERE NOT EXISTS (SELECT `username` FROM `user` WHERE `username` = 'ersks'
AND `password` = md5( 'Nepal' )) LIMIT 1
你可以使用下面的查询来创建表:
CREATE TABLE IF NOT EXISTS `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(30) NOT NULL,
`password` varchar(32) NOT NULL,
`status` tinyint(1) DEFAULT '0',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
注意:在尝试使用第一个查询之前,使用第二个查询创建表。
这不是答案,只是个便条。如果插入的值是重复的,则像接受的答案中那样的查询将不起作用,就像下面这样:
INSERT INTO `addr` (`email`, `name`)
SELECT * FROM (SELECT 'user@domain.tld', 'user@domain.tld') AS tmp
WHERE NOT EXISTS (
SELECT `email` FROM `addr` WHERE `email` LIKE 'user@domain.tld'
);
Error
SQL query: Copy Documentation
MySQL said: Documentation
#1060 - Duplicate column name 'user@domain.tld'
相反,Mahbub Tito回答的问题很好:
INSERT INTO `addr` (`email`, `name`)
SELECT 'user@domain.tld', 'user@domain.tld'
WHERE NOT EXISTS (
SELECT `email` FROM `addr` WHERE `email` LIKE 'user@domain.tld'
);
1 row inserted.
在MariaDB中测试
MySQL提供了一个非常可爱的解决方案:
REPLACE INTO `table` VALUES (5, 'John', 'Doe', SHA1('password'));
非常容易使用,因为您已经声明了一个唯一的主键(这里的值为5)。