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SQL UPDATE 语句


SQL UPDATE 语句

UPDATE语句用于修改表中的现有记录。

更新语法

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

注意:更新表中的记录时要小心!请注意UPDATE语句中的WHERE子句.WHERE子句指定应更新的记录。如果省略WHERE子句,表中的所有记录都将更新!


演示数据库

以下是Northwind示例数据库中“Customers”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 Constituciуn 2222 Mйxico D.F. 05021 Mexico
3 Antonio Moreno Taquerнa Antonio Moreno Mataderos 2312 Mйxico D.F. 05023 Mexico
4 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbkцp Christina Berglund Berguvsvдgen 8 Luleе S-958 22 Sweden

更新表

以下SQL语句使用新联系人新城市更新第一个客户(CustomerID = 1)。

实例

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

运行实例»

“Customers”表中的查询如下所示:

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 Constituciуn 2222 Mйxico D.F. 05021 Mexico
3 Antonio Moreno Taquerнa Antonio Moreno Mataderos 2312 Mйxico D.F. 05023 Mexico
4 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbkцp Christina Berglund Berguvsvдgen 8 Luleе S-958 22 Sweden

更新多个记录

它是WHERE子句,用于确定要更新的记录数。

以下SQL语句对于“Country”为“Mexico”的所有记录的联系人名称更新为“Juan”:

实例

UPDATE Customers
SET ContactName='Juan'
WHERE Country='Mexico';

运行实例»

“Customers”表中的查询如下所示:

CustomerID CustomerName ContactName Address City PostalCode Country
1 Alfreds Futterkiste Alfred Schmidt Obere Str. 57 Frankfurt 12209 Germany
2 Ana Trujillo Emparedados y helados Juan Avda. de la Constituciуn 2222 Mйxico D.F. 05021 Mexico
3 Antonio Moreno Taquerнa Juan Mataderos 2312 Mйxico D.F. 05023 Mexico
4 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbkцp Christina Berglund Berguvsvдgen 8 Luleе S-958 22 Sweden

更新警告!

更新记录时要小心。如果省略WHERE子句,则将更新所有记录!

实例

UPDATE Customers
SET ContactName='Juan';

运行实例»

“Customers”表中的查询如下所示:

CustomerID CustomerName ContactName Address City PostalCode Country
1 Alfreds Futterkiste Juan Obere Str. 57 Frankfurt 12209 Germany
2 Ana Trujillo Emparedados y helados Juan Avda. de la Constituciуn 2222 Mйxico D.F. 05021 Mexico
3 Antonio Moreno Taquerнa Juan Mataderos 2312 Mйxico D.F. 05023 Mexico
4 Around the Horn Juan 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbkцp Juan Berguvsvдgen 8 Luleе S-958 22 Sweden