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选定的行,否则所有行都将受到影响。
带WHERE子句的UPDATE查询的基本语法如下-
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。
考虑具有以下记录的CUSTOMERS表-
+----+----------+-----+-----------+----------+ | 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 | Learnfk | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+
以下查询将更新表中ID号为6的客户的地址。
SQL> UPDATE CUSTOMERS SET ADDRESS='Pune' WHERE ID=6;
现在,CUSTOMERS表将具有以下记录-
+----+----------+-----+-----------+----------+ | 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 | Learnfk | 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查询就足够了,如下面的代码块所示。
SQL> UPDATE CUSTOMERS SET ADDRESS='Pune', SALARY=1000.00;
现在,CUSTOMERS表将具有以下记录-
+----+----------+-----+---------+---------+ | 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 | Learnfk | 24 | Pune | 1000.00 | +----+----------+-----+---------+---------+
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