SQL DELETE查询用来从表中删除现有的记录。
您可以使用WHERE子句限定DELETE查询删除所选行,否则,所有的记录将被删除。
DELETE查询使用WHERE子句的基本语法如下:
DELETE FROM table_name
WHERE [condition];
您可以使用AND或OR运算符组合N多个条件。
考虑CUSTOMERS表具有以下记录:
+----+----------+-----+-----------+----------+
| 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 | MP | 4500.00 |
| 7 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+-----------+----------+
下面是一个例子,它会删除一个ID是6的客户:
SQL> DELETE FROM CUSTOMERS
WHERE ID = 6;
现在,CUSTOMERS表中有以下记录(ID=6的记录已经被删除了):
+----+----------+-----+-----------+----------+
| 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 |
| 7 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+-----------+----------+
如果你希望CUSTOMERS表中所有的记录删除,你不需要使用WHERE子句,完整的DELETE查询如下:
SQL> DELETE FROM CUSTOMERS;
现在,CUSTOMERS表将不会有任何记录。