📅 最后修改于: 2020-12-29 04:34:17 🧑 作者: Mango
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，否则所有行都会受到影响。
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 | Muffy | 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 | 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 | Muffy | 24 | Pune | 1000.00 |
+----+----------+-----+---------+---------+