SQLWhere语句

SQL WHERE 子句用于在从单个表或通过与多个表联接中获取数据时指定条件，您应该使用WHERE子句来过滤记录并仅提取必要的记录。

WHERE子句不仅在SELECT语句中使用，而且在UPDATE，DELETE语句等中使用，无涯教程将在后续章节中进行研究。

Where- 语法

带有WHERE子句的SELECT语句的基本语法如下所示。

SELECT column1, column2, columnN 
FROM table_name
WHERE [condition]

Where- 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 |
+----+----------+-----+-----------+----------+

以下代码是示例，该示例将从SALARY大于2000的CUSTOMERS表中获取ID，NAME和SALARY字段-

SQL> SELECT ID, NAME, SALARY 
FROM CUSTOMERS
WHERE SALARY > 2000;

这将产生以下输出-

+----+----------+----------+
| ID | NAME     | SALARY   |
+----+----------+----------+
|  4 | Chaitali |  6500.00 |
|  5 | Hardik   |  8500.00 |
|  6 | Komal    |  4500.00 |
|  7 | Learnfk    | 10000.00 |
+----+----------+----------+

SQL> SELECT ID, NAME, SALARY 
FROM CUSTOMERS
WHERE NAME = 'Hardik';

这将产生以下输出-

+----+----------+----------+
| ID | NAME     | SALARY   |
+----+----------+----------+
|  5 | Hardik   |  8500.00 |
+----+----------+----------+