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
您正在插入而不是更新结果。 您可以在主列中定义名称列或将其设置为惟一的。
其他回答
工作:
INSERT INTO users (full_name, login, password)
SELECT 'Mahbub Tito','tito',SHA1('12345') FROM DUAL
WHERE NOT EXISTS
(SELECT login FROM users WHERE login='tito');
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 |
+----+---------+-----------+------+
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)
insert into customer_keyskill(customerID, keySkillID)
select 2,1 from dual
where not exists (
select customerID from customer_keyskill
where customerID = 2
and keySkillID = 1 )
你可以简单地使用以下方法:
INSERT INTO ... ON DUPLICATE KEY UPDATE ...
通过这种方式，您可以插入任何新的原始数据，如果有重复的数据，则替换特定的列(最好的列是时间戳)。 例如:
CREATE TABLE IF NOT EXISTS Devices (
id INT(6) NOT NULL AUTO_INCREMENT,
unique_id VARCHAR(100) NOT NULL PRIMARY KEY,
created_at VARCHAR(100) NOT NULL,
UNIQUE KEY unique_id (unique_id),
UNIQUE KEY id (id)
)
CHARACTER SET utf8
COLLATE utf8_unicode_ci;
INSERT INTO Devices(unique_id, time)
VALUES('$device_id', '$current_time')
ON DUPLICATE KEY UPDATE time = '$current_time';
