1. 使用WHERE子句
SELECT
prod_name,
prod_price
FROM
products
WHERE
prod_price = 2.50;
2. WHERE子句操作符
操作符 |
說明 |
= |
等於 |
<> |
不等於 |
!= |
不等於 |
< |
小於 |
<= |
小於等於 |
> |
大於 |
>= |
大於等於 |
BETWEEN |
在指定的兩個值之間 |
3. 檢查單個值
SELECT
prod_name,
prod_price
FROM
products
WHERE
prod_name = 'fuses';
SELECT
prod_name,
prod_price
FROM
products
WHERE
prod_price < 10;
SELECT
prod_name,
prod_price
FROM
products
WHERE
prod_price <= 10;
4. 不匹配檢查
SELECT
vend_id,
prod_name
FROM
products
WHERE
vend_id <> 1003;
SELECT
vend_id,
prod_name
FROM
products
WHERE
vend_id != 1003;
5. 範圍值檢查
SELECT
prod_name ,
prod_price
FROM
products
WHERE
prod_price BETWEEN 5 AND 10;
6. 空值檢查
SELECT
cust_id
FROM
customers
WHERE
cust_email IS NULL;
- ( NULL無值 )與 0 和 空字符串 或者空格 不同