MySQL常用命令（三）-IN、LIKE

IN

与OR的功能相似，但是与OR相比具有更多优势

• 更简洁；
• 计算速度更快；
• 可以包含其他的SELECT语句，功能更加强大；

mysql> SELECT productName,price FROM product;
+-------------+---------+
| productName | price   |
+-------------+---------+
| 10001       |  100.00 |
| 10001       |  450.00 |
| 10002       |   30.00 |
| 10002       |  888.00 |
| 10003       | 1000.00 |
+-------------+---------+
5 rows in set (0.00 sec)

mysql> SELECT productName,price FROM product WHERE productName IN ('10001','10003');
+-------------+---------+
| productName | price   |
+-------------+---------+
| 10001       |  100.00 |
| 10001       |  450.00 |
| 10003       | 1000.00 |
+-------------+---------+
3 rows in set (0.00 sec)

mysql> SELECT productName,price FROM product WHERE productName = '10001' OR productName = '10003';
+-------------+---------+
| productName | price   |
+-------------+---------+
| 10001       |  100.00 |
| 10001       |  450.00 |
| 10003       | 1000.00 |
+-------------+---------+
3 rows in set (0.00 sec)

NOT

作用：否定它之后的任何条件；
常见的搭配：NOT IN、NOT BETWEEN、NOT EXIST、NOT NULL；

mysql> SELECT productName,price FROM product;
+-------------+---------+
| productName | price   |
+-------------+---------+
| 10001       |  100.00 |
| 10001       |  450.00 |
| 10002       |   30.00 |
| 10002       |  888.00 |
| 10003       | 1000.00 |
+-------------+---------+
5 rows in set (0.00 sec)

mysql> SELECT productName,price FROM product WHERE productName NOT  IN ('10001','10003');
+-------------+--------+
| productName | price  |
+-------------+--------+
| 10002       |  30.00 |
| 10002       | 888.00 |
+-------------+--------+
2 rows in set (0.00 sec)

LIKE

作用：进行模糊搜索；

%通配符

表示任何字符串出现任何次数；
注意：

• 在给定的位置出现0个、1个和任意多个字符
• 不可以匹配NULL；

mysql> SELECT productName,price FROM product;
+-------------+---------+
| productName | price   |
+-------------+---------+
| 10001       |  100.00 |
| 10001       |  450.00 |
| 10002       |   30.00 |
| 10002       |  888.00 |
| 10003       | 1000.00 |
+-------------+---------+
5 rows in set (0.00 sec)

mysql> SELECT productName,price FROM product WHERE productName LIKE '10001%';
+-------------+--------+
| productName | price  |
+-------------+--------+
| 10001       | 100.00 |
| 10001       | 450.00 |
+-------------+--------+
2 rows in set (0.00 sec)

mysql> SELECT productName,price FROM product WHERE productName LIKE '1000%';
+-------------+---------+
| productName | price   |
+-------------+---------+
| 10001       |  100.00 |
| 10001       |  450.00 |
| 10002       |   30.00 |
| 10002       |  888.00 |
| 10003       | 1000.00 |
+-------------+---------+
5 rows in set (0.00 sec)

mysql> SELECT productName,price FROM product WHERE productName LIKE '%001%';
+-------------+--------+
| productName | price  |
+-------------+--------+
| 10001       | 100.00 |
| 10001       | 450.00 |
+-------------+--------+
2 rows in set (0.00 sec)

_通配符

与%可以匹配任意多个字符不同，它只能匹配一个字符；

mysql> SELECT productName,price FROM product;
+-------------+---------+
| productName | price   |
+-------------+---------+
| 10001       |  100.00 |
| 10001       |  450.00 |
| 10002       |   30.00 |
| 10002       |  888.00 |
| 10003       | 1000.00 |
+-------------+---------+
5 rows in set (0.00 sec)

mysql> SELECT productName,price FROM product WHERE productName LIKE '_001';
Empty set (0.00 sec)

mysql> SELECT productName,price FROM product WHERE productName LIKE '_0001';
+-------------+--------+
| productName | price  |
+-------------+--------+
| 10001       | 100.00 |
| 10001       | 450.00 |
+-------------+--------+
2 rows in set (0.00 sec)

通配符使用的利弊

• 通配符是模糊检索，效率没有精确检索快；
• 非不要情况下，要少使用通配符进行检索；