SQL UPDATE 查询用于修改表中的现有记录.您可以将WHERE子句与UPDATE查询一起使用来更新所选行，否则所有行都会受到影响.
基本语法带有WHERE子句的UPDATE查询的结果如下 :
UPDATE table_name SET column1 = value1, column2 = value2...., columnN = valueN WHERE [condition];
您可以使用AND或OR运算符组合N个条件.
考虑CUSTOMERS表有以下记录 :
+----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | MP | 4500.00 | | 7 | Muffy | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+
以下查询将更新表中ID号为6的客户的ADDRESS.
SQL> UPDATE CUSTOMERS SET ADDRESS ='Pune' WHERE ID = 6;
现在，CUSTOMERS表将有以下记录 :
+----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | Pune | 4500.00 | | 7 | Muffy | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+
如果要修改CUSTOMERS表中的所有ADDRESS和SALARY列值，则不需要使用WHERE子句，因为UPDATE查询将足够，如下面的代码块所示.
SQL> UPDATE CUSTOMERS SET ADDRESS = 'Pune', SALARY = 1000.00;
现在，CUSTOMERS表将有以下记录 :
+----+----------+-----+---------+---------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+---------+---------+ | 1 | Ramesh | 32 | Pune | 1000.00 | | 2 | Khilan | 25 | Pune | 1000.00 | | 3 | kaushik | 23 | Pune | 1000.00 | | 4 | Chaitali | 25 | Pune | 1000.00 | | 5 | Hardik | 27 | Pune | 1000.00 | | 6 | Komal | 22 | Pune | 1000.00 | | 7 | Muffy | 24 | Pune | 1000.00 | +----+----------+-----+---------+---------+
