时间:2021-05-02
Mysql可以通过运算符来对表中数据进行运算,比如通过出生日期求年龄等 运算符包括四类,分别是:算数运算符、比较运算符、逻辑运算符和位运算符 算数运算符 加、减、乘运算 复制代码 代码如下: mysql> select a,a+5,a*2 from t1; +------+------+------+ | a | a+5 | a*2 | +------+------+------+ | 24 | 29 | 48 | +------+------+------+ row in set (0.00 sec) 这里的原值为24,后面也可以使用混合运算,只需要注意优先级即可 除法和取模运算 复制代码 代码如下: mysql> select a,a/3,a div 3,a%5,mod(a,5) from t1; +------+--------+---------+------+----------+ | a | a/3 | a div 3 | a%5 | mod(a,5) | +------+--------+---------+------+----------+ | 24 | 8.0000 | 8 | 4 | 4 | +------+--------+---------+------+----------+ row in set (0.00 sec) 此处 / 和 div 代表整除,% 和 mod 代表取模 要注意的是,如果被除数为0,那么计算结果是NULL 比较运算符 数值比较 复制代码 代码如下: mysql> select a,a=24,a<12,a>40,a>=24,a<=24,a!=24,a<>24,a<=>24 from t1; +------+------+------+------+-------+-------+-------+-------+--------+ | a | a=24 | a<12 | a>40 | a>=24 | a<=24 | a!=24 | a<>24 | a<=>24 | +------+------+------+------+-------+-------+-------+-------+--------+ | 24 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | +------+------+------+------+-------+-------+-------+-------+--------+ row in set (0.00 sec) 这里的1代表真,0代表假,需要说明的是<>和<=> <>代表不等于,等同于!= <=>代表等于,等同于= 此外,等于和不等于不仅可以比较数值,还能比较字符串 字符串比较 复制代码 代码如下: mysql> select a,a='24','ha'<>'ha','xa'='xa','b'!='b' from t1; +------+--------+------------+-----------+----------+ | a | a='24' | 'ha'<>'ha' | 'xa'='xa' | 'b'!='b' | +------+--------+------------+-----------+----------+ | 24 | 1 | 0 | 1 | 0 | +------+--------+------------+-----------+----------+ row in set (0.00 sec) is null 和is not null 复制代码 代码如下: mysql> select a,a is null, a is not null from t1; +------+-----------+---------------+ | a | a is null | a is not null | +------+-----------+---------------+ | 24 | 0 | 1 | +------+-----------+---------------+ row in set (0.00 sec) 这里可以判断是否为空,NULL也可以跟NULL比较 between and和not between and 复制代码 代码如下: mysql> select a,a between 15 and 30,a not between 15 and 30 from t1; +------+---------------------+-------------------------+ | a | a between 15 and 30 | a not between 15 and 30 | +------+---------------------+-------------------------+ | 24 | 1 | 0 | +------+---------------------+-------------------------+ row in set (0.00 sec) between and 和not between and可以判断数值是否在某一区间内 in mysql> select a,a in(1,2,23),a in(24,12,22) from t1; +------+--------------+----------------+ | a | a in(1,2,23) | a in(24,12,22) | +------+--------------+----------------+ | 24 | 0 | 1 | +------+--------------+----------------+ row in set (0.00 sec) 判断操作数是否在某一集合内 like 复制代码 代码如下: mysql> select s,s like 'beijing',s like 'b%g',s like 'bei____',s like '%jing' from t2; +---------+------------------+--------------+------------------+----------------+ | s | s like 'beijing' | s like 'b%g' | s like 'bei____' | s like '%jing' | +---------+------------------+--------------+------------------+----------------+ | beijing | 1 | 1 | 1 | 1 | +---------+------------------+--------------+------------------+----------------+ row in set (0.00 sec) ike可以用来匹配字符串,_代表单个字符,%代表多个字符 逻辑运算符 与运算 复制代码 代码如下: mysql> select 2&&2,2&&null,2 and 3,2 and 2; +------+---------+---------+---------+ | 2&&2 | 2&&null | 2 and 3 | 2 and 2 | +------+---------+---------+---------+ | 1 | NULL | 1 | 1 | +------+---------+---------+---------+ row in set (0.00 sec) 这里&&和and意思一样 或运算 复制代码 代码如下: mysql> select 2||2,2||null,2 or 3,2 or 0; +------+---------+--------+--------+ | 2||2 | 2||null | 2 or 3 | 2 or 0 | +------+---------+--------+--------+ | 1 | 1 | 1 | 1 | +------+---------+--------+--------+ row in set (0.00 sec) 这里||和or的意思一样 非运算 复制代码 代码如下:
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前言mysql中有4类运算符,它们是:算术运算符比较运算符逻辑运算符位操作运算符这个大家应该都比较熟悉,但本文给大家总结介绍的关于MySql中特殊运算符的相关内
在C#中常用到的运算符有条件运算符,is运算符,as运算符,typeof运算符等等,接下来在文章中将为大家具体介绍各个运算符的使用方法条件运算符条件运算符用(&
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C++中运算符&和&&、|和||的详解及区别简介:&&是逻辑与运算符,||是逻辑或运算符,都是逻辑运算符,两边只能是bool类型&与|既可以进行逻辑运算,又可以
一、运算符算术运算符:+-*/可以在select语句中使用连接运算符:||selectdeptno||dnamefromdept;比较运算符:>>==!=<