SQL - 更新操作(Update)

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。

Update Query - 语法

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。

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Update Query - 示例

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 |
+----+----------+-----+---------+---------+