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
INSERT IGNORE INTO `mytable`
SET `field0` = '2',
`field1` = 12345,
`field2` = 12678;
这里的mysql查询，即插入记录，如果不存在，将忽略现有的类似记录。
----Untested----
其他回答
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
我遇到了一个问题，迈克建议的方法部分有效，我有一个错误复制列名= '0'，并更改了您的查询的语法如下'
$tQ = "INSERT INTO names (name_id, surname_id, sum, sum2, sum3,sum4,sum5)
SELECT '$name', '$surname', '$sum', '$sum2', '$sum3','$sum4','$sum5'
FROM DUAL
WHERE NOT EXISTS (
SELECT sum FROM names WHERE name_id = '$name'
AND surname_id = '$surname') LIMIT 1;";
问题出在列名上。sum3等于sum4, mysql抛出重复的列名，我用这种语法写了代码，它工作得很好，
INSERT不允许语法中的WHERE。
你可以做的是:在字段上创建一个UNIQUE INDEX，它应该是唯一的(name)，然后使用:
正常插入(如果名称已经存在，则处理错误) INSERT IGNORE(如果name已经存在，将无声失败，导致警告(而不是错误)) 插入……ON DUPLICATE KEY UPDATE(如果名称已经存在，将在末尾执行UPDATE，请参阅文档)
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)。
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 |
+----+---------+-----------+------+
