SQL 教程SQL 简介SQL 语法SQL数据类型SQL操运算符SQL表达式SQL创建数据库(CREATE DATABASE)SQL丢弃或删除数据库SQL选择数据库SQL创建表(CREATE Table)SQL删除表(DROP或DELETE Table)SQL INSERT INTO插入查询SQL SELECT查询语句SQL WHERE子句SQL AND和OR运算符SQL UPDATE更新查询SQL DELETE删除查询SQL LIKE子句SQL TOP,LIMIT,ROWNUM子句SQL ORDER BY排序子句SQL GROUP BY(分组)SQL Distinct关键字SQL排序结果SQL NULL值SQL约束SQL Join联接SQL UNION子句/操作符SQL别名语法SQL索引SQL ALTER TABLE（修改表）SQL TRUNCATE TABLE(截断表)SQL View(视图)SQL Having子句SQL事务SQL通配符运算符SQL日期函数SQL临时表SQL克隆表SQL子查询SQL使用序列（自动递增）SQL DISTINCT重复处理SQL注入SQL实用函数
SQL操运算符
什么是SQL运算符？
运算符是一个保留字或主要在SQL语句的WHERE子句用来执行操作使用的字符，如比较和算术运算。
运算符用于指定在SQL语句中的条件，并作为连词在一份声明中多个条件。
算术运算符
比较运算符
逻辑运算符
用于否定条件运算符
SQL算术运算符：
假设变量a=10和变量b=20，则：
这里是显示SQL算术运算符的使用简单的例子：
SQL> select 10+ 20;
+--------+
| 10+ 20 |
+--------+
| 30 |
+--------+
1 row in set (0.00 sec)
SQL> select 10 * 20;
+---------+
| 10 * 20 |
+---------+
| 200 |
+---------+
1 row in set (0.00 sec)
SQL> select 10 / 5;
+--------+
| 10 / 5 |
+--------+
| 2.0000 |
+--------+
1 row in set (0.03 sec)
SQL> select 12 % 5;
+---------+
| 12 % 5 |
+---------+
| 2 |
+---------+
1 row in set (0.00 sec)| 运算符 | 描述 | 实例 |
|---|---|---|
| + | 加法 - 操作符两边将值 | a + b = 30 |
| - | 减法 - 从左手操作数减去右手操作数 | a - b = -10 |
| * | 乘法 - 操作符两边相乘的值 | a * b = 200 |
| / | 除法 - 由右手操作除以左手操作数 | b / a = 2 |
| % | 模 - 由右手操作数除以左手操作并返回余数 | b % a = 0 |
SQL比较运算符：
假设变量a=10和变量b=20，则：
SQL> SELECT * FROM CUSTOMERS;
+----+----------+-----+-----------+----------+
| 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 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+-----------+----------+
7 rows in set (0.00 sec)这里是显示SQL比较操作的使用简单的例子：
SQL> SELECT * FROM CUSTOMERS WHERE SALARY > 5000;
+----+----------+-----+---------+----------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+---------+----------+
| 4 | Chaitali | 25 | Mumbai | 6500.00 |
| 5 | Hardik | 27 | Bhopal | 8500.00 |
| 7 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+---------+----------+
3 rows in set (0.00 sec)
SQL> SELECT * FROM CUSTOMERS WHERE SALARY = 2000;
+----+---------+-----+-----------+---------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+---------+-----+-----------+---------+
| 1 | Ramesh | 32 | Ahmedabad | 2000.00 |
| 3 | kaushik | 23 | Kota | 2000.00 |
+----+---------+-----+-----------+---------+
2 rows in set (0.00 sec)
SQL> SELECT * FROM CUSTOMERS WHERE SALARY != 2000;
+----+----------+-----+---------+----------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+---------+----------+
| 2 | Khilan | 25 | Delhi | 1500.00 |
| 4 | Chaitali | 25 | Mumbai | 6500.00 |
| 5 | Hardik | 27 | Bhopal | 8500.00 |
| 6 | Komal | 22 | MP | 4500.00 |
| 7 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+---------+----------+
5 rows in set (0.00 sec)
SQL> SELECT * FROM CUSTOMERS WHERE SALARY <> 2000;
+----+----------+-----+---------+----------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+---------+----------+
| 2 | Khilan | 25 | Delhi | 1500.00 |
| 4 | Chaitali | 25 | Mumbai | 6500.00 |
| 5 | Hardik | 27 | Bhopal | 8500.00 |
| 6 | Komal | 22 | MP | 4500.00 |
| 7 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+---------+----------+
5 rows in set (0.00 sec)
SQL> SELECT * FROM CUSTOMERS WHERE SALARY >= 6500;
+----+----------+-----+---------+----------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+---------+----------+
| 4 | Chaitali | 25 | Mumbai | 6500.00 |
| 5 | Hardik | 27 | Bhopal | 8500.00 |
| 7 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+---------+----------+
3 rows in set (0.00 sec)| 运算符 | 描述 | 实例 |
|---|---|---|
| = | 检查是否两个操作数的值相等，如果是的话那么条件为真 | (a = b) 不为 true. |
| != | 检查是否两个操作数的值相等，如果值不相等，则条件变为真 | (a != b) 为 true. |
| <> | 检查是否两个操作数的值相等，如果值不相等，则条件变为真 | (a <> b) 为 true. |
| > | 检查左边的操作数的值是否大于右操作数的值，如果是的话那么条件为真 | (a > b) 不为 true. |
| < | 检查左边的操作数的值是否小于右操作数的值，如果是的话那么条件为真 | (a < b) 为 true. |
| >= | 检查左边的操作数的值是否大于或等于右操作数的值，如果是的话那么条件为真 | (a >= b) 不为 true. |
| <= | 检查左边的操作数的值是否小于或等于右操作数的值，如果是的话那么条件为真 | (a <= b) 为 true. |
| !< | 检查左边的操作数的值是否不小于右操作数的值较小，如果是的话那么条件为真 | (a !< b) 为 false. |
| !> | 检查左边的操作数的值是否不小于右操作数的值越大，如果是的话那么条件为真 | (a !> b) 为 true. |
SQL逻辑运算符：
这里是所有SQL中可用的逻辑运算符的列表。
SQL> SELECT * FROM CUSTOMERS;
+----+----------+-----+-----------+----------+
| 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 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+-----------+----------+
7 rows in set (0.00 sec)这里是显示SQL比较操作的使用简单的例子：
SQL> SELECT * FROM CUSTOMERS WHERE AGE >= 25 AND SALARY >= 6500;
+----+----------+-----+---------+---------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+---------+---------+
| 4 | Chaitali | 25 | Mumbai | 6500.00 |
| 5 | Hardik | 27 | Bhopal | 8500.00 |
+----+----------+-----+---------+---------+
2 rows in set (0.00 sec)
SQL> SELECT * FROM CUSTOMERS WHERE AGE >= 25 OR SALARY >= 6500;
+----+----------+-----+-----------+----------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+-----------+----------+
| 1 | Ramesh | 32 | Ahmedabad | 2000.00 |
| 2 | Khilan | 25 | Delhi | 1500.00 |
| 4 | Chaitali | 25 | Mumbai | 6500.00 |
| 5 | Hardik | 27 | Bhopal | 8500.00 |
| 7 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+-----------+----------+
5 rows in set (0.00 sec)
SQL> SELECT * FROM CUSTOMERS WHERE AGE IS NOT NULL;
+----+----------+-----+-----------+----------+
| 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 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+-----------+----------+
7 rows in set (0.00 sec)
SQL> SELECT * FROM CUSTOMERS WHERE NAME LIKE 'Ko%';
+----+-------+-----+---------+---------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+-------+-----+---------+---------+
| 6 | Komal | 22 | MP | 4500.00 |
+----+-------+-----+---------+---------+
1 row in set (0.00 sec)
SQL> SELECT * FROM CUSTOMERS WHERE AGE IN ( 25, 27 );
+----+----------+-----+---------+---------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+---------+---------+
| 2 | Khilan | 25 | Delhi | 1500.00 |
| 4 | Chaitali | 25 | Mumbai | 6500.00 |
| 5 | Hardik | 27 | Bhopal | 8500.00 |
+----+----------+-----+---------+---------+
3 rows in set (0.00 sec)
SQL> SELECT * FROM CUSTOMERS WHERE AGE BETWEEN 25 AND 27;
+----+----------+-----+---------+---------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+---------+---------+
| 2 | Khilan | 25 | Delhi | 1500.00 |
| 4 | Chaitali | 25 | Mumbai | 6500.00 |
| 5 | Hardik | 27 | Bhopal | 8500.00 |
+----+----------+-----+---------+---------+
3 rows in set (0.00 sec)
SQL> SELECT AGE FROM CUSTOMERS
WHERE EXISTS (SELECT AGE FROM CUSTOMERS WHERE SALARY > 6500);
+-----+
| AGE |
+-----+
| 32 |
| 25 |
| 23 |
| 25 |
| 27 |
| 22 |
| 24 |
+-----+
7 rows in set (0.02 sec)
SQL> SELECT * FROM CUSTOMERS
WHERE AGE > ALL (SELECT AGE FROM CUSTOMERS WHERE SALARY > 6500);
+----+--------+-----+-----------+---------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+--------+-----+-----------+---------+
| 1 | Ramesh | 32 | Ahmedabad | 2000.00 |
+----+--------+-----+-----------+---------+
1 row in set (0.02 sec)
SQL> SELECT * FROM CUSTOMERS
WHERE AGE > ANY (SELECT AGE FROM CUSTOMERS WHERE SALARY > 6500);
+----+----------+-----+-----------+---------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+-----------+---------+
| 1 | Ramesh | 32 | Ahmedabad | 2000.00 |
| 2 | Khilan | 25 | Delhi | 1500.00 |
| 4 | Chaitali | 25 | Mumbai | 6500.00 |
| 5 | Hardik | 27 | Bhopal | 8500.00 |
+----+----------+-----+-----------+---------+
4 rows in set (0.00 sec)| 操作符 | 描述 |
|---|---|
| ALL | ALL运算符是用来在另一个值设定比较值的所有值 |
| AND | AND运算允许多个条件在SQL语句中，存在WHERE子句 |
| ANY | ANY运算符用于根据条件在列表中的值进行比较的任何应用值 |
| BETWEEN | BETWEEN运算符用于搜索是在一组值的那个值，给定的最小值和最大值 |
| EXISTS | EXISTS运算符用于搜索行中指定的表，以满足某些标准的存在 |
| IN | IN运算符用于一个值进行比较，以已被指定的文字值的列表 |
| LIKE | LIKE运算符用来比较使用通配符运算符相似的值 |
| NOT | NOT运算符反转与它被使用的逻辑运算器的含义。例如：NOT EXISTS，NOT BETWEEN，NOT IN等，这是一个否定运算符 |
| OR | OR运算符是用来多个条件WHERE子句结合起来的SQL语句 |
| IS NULL | NULL运算符用来比较一个NULL值 |
| UNIQUE | UNIQUE操作搜索指定表的每一行的唯一性（不重复） |