MySQL UPDATE

创建于 2024-12-02 / 26

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MySQL UPDATE 语句

UPDATE语句用于修改表中已有的记录。

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

注意:更新表中的记录时要小心！注意 UPDATE 语句中的 WHERE 子句。 WHERE 子句指定应该更新哪些记录。如果省略WHERE子句，表中的所有记录都会更新！

以下是 Northwind 示例数据库中 "Customers" 客户表的选择:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK

以下 SQL 语句将第一个客户 (CustomerID = 1) 更新为一个新联系人和一个新城市。

UPDATE Customers
SET ContactName = 'Alfred Schmidt', City = 'Frankfurt'
WHERE CustomerID = 1;

"客户"表中的选择现在如下所示:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Alfred Schmidt	Obere Str. 57	Frankfurt	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK

-->

WHERE 子句决定要更新多少记录。

以下 SQL 语句将所有地区为"墨西哥"的记录的 PostalCode 更新为 00000:

UPDATE Customers
SET PostalCode = 00000
WHERE Country = 'Mexico';

"Customers"表中的选择现在如下所示:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Alfred Schmidt	Obere Str. 57	Frankfurt	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	00000	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	00000	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK

更新记录时要小心。如果省略 WHERE 子句，所有记录都会更新！

UPDATE Customers
SET PostalCode = 00000;

"Customers"表中的选择现在如下所示:

CustomerID	CustomerName	ContactName	Address	City	Country
1	Alfreds Futterkiste	Alfred Schmidt	Obere Str. 57	Frankfurt	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	UK

更新 Customers 表中所有记录的 City 列。

 Customers
 City = 'Oslo';

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