文章目录

相等测试where子句操作符总结

相等测试

mysql> select prod_name,prod_price -> from products -> where prod_price = 3.49; +---------------------+------------+ | prod_name | prod_price | +---------------------+------------+ | Fish bean bag toy | 3.49 | | Bird bean bag toy | 3.49 | | Rabbit bean bag toy | 3.49 | +---------------------+------------+ 3 rows in set (0.00 sec)

where子句操作符

mysql> select prod_name, prod_price -> from products -> where prod_name = 'fuses'; Empty set (0.00 sec)

注意相等测试不是用==，就用赋值符号，这和其他语言都不一样

不匹配测试

mysql> select prod_name, prod_price -> from products -> where prod_name <> 'fuses'; +---------------------+------------+ | prod_name | prod_price | +---------------------+------------+ | Fish bean bag toy | 3.49 | | Bird bean bag toy | 3.49 | | Rabbit bean bag toy | 3.49 | | 8 inch teddy bear | 5.99 | | 12 inch teddy bear | 8.99 | | 18 inch teddy bear | 11.99 | | Raggedy Ann | 4.99 | | King doll | 9.49 | | Queen doll | 9.49 | +---------------------+------------+ 9 rows in set (0.00 sec)

范围值检查

mysql> select prod_name, prod_price -> from products -> where prod_price between 3 and 8; +---------------------+------------+ | prod_name | prod_price | +---------------------+------------+ | Fish bean bag toy | 3.49 | | Bird bean bag toy | 3.49 | | Rabbit bean bag toy | 3.49 | | 8 inch teddy bear | 5.99 | | Raggedy Ann | 4.99 | +---------------------+------------+ 5 rows in set (0.00 sec)

空值检查

mysql> select prod_name, prod_price -> from products -> where prod_price is null; Empty set (0.00 sec)

总结

order by子句必须在where子句之后