MySQL 运算符

MySQL 运算符本章节我们主要介绍 MySQL 的运算符及运算符的优先级。MySQL 主要有以下几种运算符：算术运算符比较运算符逻辑运算符位运算符算术运算符MySQL 支持的算术运算符包括: 运算符作用+加法-减法*乘法/ 或 DIV除法% 或 MOD取余在除法运算和模运算中，如果除数为0，将是非法除数，返回结果为NULL。1、加 mysql> select 1+2;+-----+| 1+2 |+-----+| 3 |+-----+2、减mysql> select 1-2;+-----+| 1-2 |+-----+| -1 |+-----+3、乘mysql> select 2*3;+-----+| 2*3 |+-----+| 6 |+-----+4、除mysql> select 2/3;+--------+| 2/3 |+--------+| 0.6667 |+--------+5、商mysql> select 10 DIV 4;+----------+| 10 DIV 4 |+----------+| 2 |+----------+6、取余mysql> select 10 MOD 4;+----------+| 10 MOD 4 |+----------+| 2 |+----------+比较运算符SELECT语句中的条件语句经常要使用比较运算符。通过这些比较运算符，可以判断表中的哪些记录是符合条件的。比较结果为真，则返回 1，为假则返回 0，比较结果不确定则返回 NULL。符号描述备注=等于<>, !=不等于>大于<小于<=小于>=大于等于BETWEEN在两值之间>=min&&<=maxNOT BETWEEN不在两值之间IN在集合中NOT IN不在集合中<=>严格比较两个NULL值是否相等两个操作码均为NULL时，其所得值为1；而当一个操作码为NULL时，其所得值为0LIKE模糊匹配REGEXP 或 RLIKE正则式匹配IS NULL为空IS NOT NULL不为空1、等于mysql> select 2=3;+-----+| 2=3 |+-----+| 0 |+-----+mysql> select NULL = NULL;+-------------+| NULL = NULL |+-------------+| NULL |+-------------+2、不等于mysql> select 2<>3;+------+| 2<>3 |+------+| 1 |+------+3、安全等于与 = 的区别在于当两个操作码均为 NULL 时，其所得值为 1 而不为 NULL，而当一个操作码为 NULL 时，其所得值为 0而不为 NULL。mysql> select 2<=>3;+-------+| 2<=>3 |+-------+| 0 |+-------+mysql> select null=null;+-----------+| null=null |+-----------+| NULL |+-----------+ mysql> select null<=>null;+-------------+| null<=>null |+-------------+| 1 |+-------------+4、小于mysql> select 2<3;+-----+| 2<3 |+-----+| 1 |+-----+5、小于等于mysql> select 2<=3;+------+| 2<=3 |+------+| 1 |+------+6、大于mysql> select 2>3;+-----+| 2>3 |+-----+| 0 |+-----+7、大于等于mysql> select 2>=3;+------+| 2>=3 |+------+| 0 |+------+8、BETWEENmysql> select 5 between 1 and 10;+--------------------+| 5 between 1 and 10 |+--------------------+| 1 |+--------------------+9、INmysql> select 5 in (1,2,3,4,5);+------------------+| 5 in (1,2,3,4,5) |+------------------+| 1 |+------------------+10、NOT INmysql> select 5 not in (1,2,3,4,5);+----------------------+| 5 not in (1,2,3,4,5) |+----------------------+| 0 |+----------------------+11、IS NULLmysql> select null is NULL;+--------------+| null is NULL |+--------------+| 1 |+--------------+mysql> select 'a' is NULL;+-------------+| 'a' is NULL |+-------------+| 0 |+-------------+12、IS NOT NULLmysql> select null IS NOT NULL;+------------------+| null IS NOT NULL |+------------------+| 0 |+------------------+ mysql> select 'a' IS NOT NULL;+-----------------+| 'a' IS NOT NULL |+-----------------+| 1 |+-----------------+13、LIKEmysql> select '12345' like '12%';+--------------------+| '12345' like '12%' |+--------------------+| 1 |+--------------------+mysql> select '12345' like '12_';+--------------------+| '12345' like '12_' |+--------------------+| 0 |+--------------------+14、REGEXPmysql> select 'beijing' REGEXP 'jing';+-------------------------+| 'beijing' REGEXP 'jing' |+-------------------------+| 1 |+-------------------------+mysql> select 'beijing' REGEXP 'xi';+-----------------------+| 'beijing' REGEXP 'xi' |+-----------------------+| 0 |+-----------------------+逻辑运算符逻辑运算符用来判断表达式的真假。如果表达式是真，结果返回 1。如果表达式是假，结果返回 0。运算符号作用NOT 或 !逻辑非AND逻辑与OR逻辑或XOR逻辑异或1、与mysql> select 2 and 0;+---------+| 2 and 0 |+---------+| 0 |+---------+ mysql> select 2 and 1; +---------+ | 2 and 1 | +---------+ | 1 | +---------+2、或mysql> select 2 or 0;+--------+| 2 or 0 |+--------+| 1 |+--------+mysql> select 2 or 1;+--------+| 2 or 1 |+--------+| 1 |+--------+mysql> select 0 or 0;+--------+| 0 or 0 |+--------+| 0 |+--------+mysql> select 1 || 0;+--------+| 1 || 0 |+--------+| 1 |+--------+3、非mysql> select not 1;+-------+| not 1 |+-------+| 0 |+-------+mysql> select !0;+----+| !0 |+----+| 1 |+----+4、异或mysql> select 1 xor 1;+---------+| 1 xor 1 |+---------+| 0 |+---------+mysql> select 0 xor 0;+---------+| 0 xor 0 |+---------+| 0 |+---------+mysql> select 1 xor 0;+---------+| 1 xor 0 |+---------+| 1 |+---------+mysql> select null or 1;+-----------+| null or 1 |+-----------+| 1 |+-----------+mysql> select 1 ^ 0;+-------+| 1 ^ 0 |+-------+| 1 |+-------+位运算符位运算符是在二进制数上进行计算的运算符。位运算会先将操作数变成二进制数，进行位运算。然后再将计算结果从二进制数变回十进制数。运算符号作用&按位与|按位或^按位异或!取反<<左移>>右移1、按位与mysql> select 3&5;+-----+| 3&5 |+-----+| 1 |+-----+2、按位或mysql> select 3|5;+-----+| 3