mysql中用来取余数的函数是_MySQL常用函数-单行处理函数-字符串处理函数(更新中...)...

本篇文章用到的数据库表

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CREATE DATABASE /*!32312 IF NOT EXISTS*/`myemployees` /*!40100 DEFAULT CHARACTER SET utf8 */;USE `myemployees`;/*Table structure for table `employees` */DROP TABLE IF EXISTS `employees`;CREATE TABLE `employees` (`employee_id` int(6) NOT NULL AUTO_INCREMENT,`first_name` varchar(20) DEFAULT NULL,`last_name` varchar(25) DEFAULT NULL,`email` varchar(25) DEFAULT NULL,`phone_number` varchar(20) DEFAULT NULL,`job_id` varchar(10) DEFAULT NULL,`salary` double(10,2) DEFAULT NULL,`commission_pct` double(4,2) DEFAULT NULL,`manager_id` int(6) DEFAULT NULL,`department_id` int(4) DEFAULT NULL,`hiredate` datetime DEFAULT NULL,PRIMARY KEY (`employee_id`),KEY `dept_id_fk` (`department_id`),KEY `job_id_fk` (`job_id`),CONSTRAINT `dept_id_fk` FOREIGN KEY (`department_id`) REFERENCES `departments` (`department_id`),CONSTRAINT `job_id_fk` FOREIGN KEY (`job_id`) REFERENCES `jobs` (`job_id`)
) ENGINE=InnoDB AUTO_INCREMENT=209 DEFAULT CHARSET=utf8;/*Data for the table `employees` */insert  into `employees`(`employee_id`,`first_name`,`last_name`,`email`,`phone_number`,`job_id`,`salary`,`commission_pct`,`manager_id`,`department_id`,`hiredate`) values (100,'Steven','K_ing','SKING','515.123.4567','AD_PRES',24000.00,NULL,NULL,90,'1992-04-03 00:00:00'),(101,'Neena','Kochhar','NKOCHHAR','515.123.4568','AD_VP',17000.00,NULL,100,90,'1992-04-03 00:00:00'),(102,'Lex','De Haan','LDEHAAN','515.123.4569','AD_VP',17000.00,NULL,100,90,'1992-04-03 00:00:00'),(103,'Alexander','Hunold','AHUNOLD','590.423.4567','IT_PROG',9000.00,NULL,102,60,'1992-04-03 00:00:00'),(104,'Bruce','Ernst','BERNST','590.423.4568','IT_PROG',6000.00,NULL,103,60,'1992-04-03 00:00:00'),(105,'David','Austin','DAUSTIN','590.423.4569','IT_PROG',4800.00,NULL,103,60,'1998-03-03 00:00:00'),(106,'Valli','Pataballa','VPATABAL','590.423.4560','IT_PROG',4800.00,NULL,103,60,'1998-03-03 00:00:00'),(107,'Diana','Lorentz','DLORENTZ','590.423.5567','IT_PROG',4200.00,NULL,103,60,'1998-03-03 00:00:00'),(108,'Nancy','Greenberg','NGREENBE','515.124.4569','FI_MGR',12000.00,NULL,101,100,'1998-03-03 00:00:00'),(109,'Daniel','Faviet','DFAVIET','515.124.4169','FI_ACCOUNT',9000.00,NULL,108,100,'1998-03-03 00:00:00'),(110,'John','Chen','JCHEN','515.124.4269','FI_ACCOUNT',8200.00,NULL,108,100,'2000-09-09 00:00:00'),(111,'Ismael','Sciarra','ISCIARRA','515.124.4369','FI_ACCOUNT',7700.00,NULL,108,100,'2000-09-09 00:00:00'),(112,'Jose Manuel','Urman','JMURMAN','515.124.4469','FI_ACCOUNT',7800.00,NULL,108,100,'2000-09-09 00:00:00'),(113,'Luis','Popp','LPOPP','515.124.4567','FI_ACCOUNT',6900.00,NULL,108,100,'2000-09-09 00:00:00'),(114,'Den','Raphaely','DRAPHEAL','515.127.4561','PU_MAN',11000.00,NULL,100,30,'2000-09-09 00:00:00'),(115,'Alexander','Khoo','AKHOO','515.127.4562','PU_CLERK',3100.00,NULL,114,30,'2000-09-09 00:00:00'),(116,'Shelli','Baida','SBAIDA','515.127.4563','PU_CLERK',2900.00,NULL,114,30,'2000-09-09 00:00:00'),(117,'Sigal','Tobias','STOBIAS','515.127.4564','PU_CLERK',2800.00,NULL,114,30,'2000-09-09 00:00:00'),(118,'Guy','Himuro','GHIMURO','515.127.4565','PU_CLERK',2600.00,NULL,114,30,'2000-09-09 00:00:00'),(119,'Karen','Colmenares','KCOLMENA','515.127.4566','PU_CLERK',2500.00,NULL,114,30,'2000-09-09 00:00:00'),(120,'Matthew','Weiss','MWEISS','650.123.1234','ST_MAN',8000.00,NULL,100,50,'2004-02-06 00:00:00'),(121,'Adam','Fripp','AFRIPP','650.123.2234','ST_MAN',8200.00,NULL,100,50,'2004-02-06 00:00:00'),(122,'Payam','Kaufling','PKAUFLIN','650.123.3234','ST_MAN',7900.00,NULL,100,50,'2004-02-06 00:00:00'),(123,'Shanta','Vollman','SVOLLMAN','650.123.4234','ST_MAN',6500.00,NULL,100,50,'2004-02-06 00:00:00'),(124,'Kevin','Mourgos','KMOURGOS','650.123.5234','ST_MAN',5800.00,NULL,100,50,'2004-02-06 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00:00:00'),(134,'Michael','Rogers','MROGERS','650.127.1834','ST_CLERK',2900.00,NULL,122,50,'2002-12-23 00:00:00'),(135,'Ki','Gee','KGEE','650.127.1734','ST_CLERK',2400.00,NULL,122,50,'2002-12-23 00:00:00'),(136,'Hazel','Philtanker','HPHILTAN','650.127.1634','ST_CLERK',2200.00,NULL,122,50,'2002-12-23 00:00:00'),(137,'Renske','Ladwig','RLADWIG','650.121.1234','ST_CLERK',3600.00,NULL,123,50,'2002-12-23 00:00:00'),(138,'Stephen','Stiles','SSTILES','650.121.2034','ST_CLERK',3200.00,NULL,123,50,'2002-12-23 00:00:00'),(139,'John','Seo','JSEO','650.121.2019','ST_CLERK',2700.00,NULL,123,50,'2002-12-23 00:00:00'),(140,'Joshua','Patel','JPATEL','650.121.1834','ST_CLERK',2500.00,NULL,123,50,'2002-12-23 00:00:00'),(141,'Trenna','Rajs','TRAJS','650.121.8009','ST_CLERK',3500.00,NULL,124,50,'2002-12-23 00:00:00'),(142,'Curtis','Davies','CDAVIES','650.121.2994','ST_CLERK',3100.00,NULL,124,50,'2002-12-23 00:00:00'),(143,'Randall','Matos','RMATOS','650.121.2874','ST_CLERK',2600.00,NULL,124,50,'2002-12-23 00:00:00'),(144,'Peter','Vargas','PVARGAS','650.121.2004','ST_CLERK',2500.00,NULL,124,50,'2002-12-23 00:00:00'),(145,'John','Russell','JRUSSEL','011.44.1344.429268','SA_MAN',14000.00,0.40,100,80,'2002-12-23 00:00:00'),(146,'Karen','Partners','KPARTNER','011.44.1344.467268','SA_MAN',13500.00,0.30,100,80,'2002-12-23 00:00:00'),(147,'Alberto','Errazuriz','AERRAZUR','011.44.1344.429278','SA_MAN',12000.00,0.30,100,80,'2002-12-23 00:00:00'),(148,'Gerald','Cambrault','GCAMBRAU','011.44.1344.619268','SA_MAN',11000.00,0.30,100,80,'2002-12-23 00:00:00'),(149,'Eleni','Zlotkey','EZLOTKEY','011.44.1344.429018','SA_MAN',10500.00,0.20,100,80,'2002-12-23 00:00:00'),(150,'Peter','Tucker','PTUCKER','011.44.1344.129268','SA_REP',10000.00,0.30,145,80,'2014-03-05 00:00:00'),(151,'David','Bernstein','DBERNSTE','011.44.1344.345268','SA_REP',9500.00,0.25,145,80,'2014-03-05 00:00:00'),(152,'Peter','Hall','PHALL','011.44.1344.478968','SA_REP',9000.00,0.25,145,80,'2014-03-05 00:00:00'),(153,'Christopher','Olsen','COLSEN','011.44.1344.498718','SA_REP',8000.00,0.20,145,80,'2014-03-05 00:00:00'),(154,'Nanette','Cambrault','NCAMBRAU','011.44.1344.987668','SA_REP',7500.00,0.20,145,80,'2014-03-05 00:00:00'),(155,'Oliver','Tuvault','OTUVAULT','011.44.1344.486508','SA_REP',7000.00,0.15,145,80,'2014-03-05 00:00:00'),(156,'Janette','K_ing','JKING','011.44.1345.429268','SA_REP',10000.00,0.35,146,80,'2014-03-05 00:00:00'),(157,'Patrick','Sully','PSULLY','011.44.1345.929268','SA_REP',9500.00,0.35,146,80,'2014-03-05 00:00:00'),(158,'Allan','McEwen','AMCEWEN','011.44.1345.829268','SA_REP',9000.00,0.35,146,80,'2014-03-05 00:00:00'),(159,'Lindsey','Smith','LSMITH','011.44.1345.729268','SA_REP',8000.00,0.30,146,80,'2014-03-05 00:00:00'),(160,'Louise','Doran','LDORAN','011.44.1345.629268','SA_REP',7500.00,0.30,146,80,'2014-03-05 00:00:00'),(161,'Sarath','Sewall','SSEWALL','011.44.1345.529268','SA_REP',7000.00,0.25,146,80,'2014-03-05 00:00:00'),(162,'Clara','Vishney','CVISHNEY','011.44.1346.129268','SA_REP',10500.00,0.25,147,80,'2014-03-05 00:00:00'),(163,'Danielle','Greene','DGREENE','011.44.1346.229268','SA_REP',9500.00,0.15,147,80,'2014-03-05 00:00:00'),(164,'Mattea','Marvins','MMARVINS','011.44.1346.329268','SA_REP',7200.00,0.10,147,80,'2014-03-05 00:00:00'),(165,'David','Lee','DLEE','011.44.1346.529268','SA_REP',6800.00,0.10,147,80,'2014-03-05 00:00:00'),(166,'Sundar','Ande','SANDE','011.44.1346.629268','SA_REP',6400.00,0.10,147,80,'2014-03-05 00:00:00'),(167,'Amit','Banda','ABANDA','011.44.1346.729268','SA_REP',6200.00,0.10,147,80,'2014-03-05 00:00:00'),(168,'Lisa','Ozer','LOZER','011.44.1343.929268','SA_REP',11500.00,0.25,148,80,'2014-03-05 00:00:00'),(169,'Harrison','Bloom','HBLOOM','011.44.1343.829268','SA_REP',10000.00,0.20,148,80,'2014-03-05 00:00:00'),(170,'Tayler','Fox','TFOX','011.44.1343.729268','SA_REP',9600.00,0.20,148,80,'2014-03-05 00:00:00'),(171,'William','Smith','WSMITH','011.44.1343.629268','SA_REP',7400.00,0.15,148,80,'2014-03-05 00:00:00'),(172,'Elizabeth','Bates','EBATES','011.44.1343.529268','SA_REP',7300.00,0.15,148,80,'2014-03-05 00:00:00'),(173,'Sundita','Kumar','SKUMAR','011.44.1343.329268','SA_REP',6100.00,0.10,148,80,'2014-03-05 00:00:00'),(174,'Ellen','Abel','EABEL','011.44.1644.429267','SA_REP',11000.00,0.30,149,80,'2014-03-05 00:00:00'),(175,'Alyssa','Hutton','AHUTTON','011.44.1644.429266','SA_REP',8800.00,0.25,149,80,'2014-03-05 00:00:00'),(176,'Jonathon','Taylor','JTAYLOR','011.44.1644.429265','SA_REP',8600.00,0.20,149,80,'2014-03-05 00:00:00'),(177,'Jack','Livingston','JLIVINGS','011.44.1644.429264','SA_REP',8400.00,0.20,149,80,'2014-03-05 00:00:00'),(178,'Kimberely','Grant','KGRANT','011.44.1644.429263','SA_REP',7000.00,0.15,149,NULL,'2014-03-05 00:00:00'),(179,'Charles','Johnson','CJOHNSON','011.44.1644.429262','SA_REP',6200.00,0.10,149,80,'2014-03-05 00:00:00'),(180,'Winston','Taylor','WTAYLOR','650.507.9876','SH_CLERK',3200.00,NULL,120,50,'2014-03-05 00:00:00'),(181,'Jean','Fleaur','JFLEAUR','650.507.9877','SH_CLERK',3100.00,NULL,120,50,'2014-03-05 00:00:00'),(182,'Martha','Sullivan','MSULLIVA','650.507.9878','SH_CLERK',2500.00,NULL,120,50,'2014-03-05 00:00:00'),(183,'Girard','Geoni','GGEONI','650.507.9879','SH_CLERK',2800.00,NULL,120,50,'2014-03-05 00:00:00'),(184,'Nandita','Sarchand','NSARCHAN','650.509.1876','SH_CLERK',4200.00,NULL,121,50,'2014-03-05 00:00:00'),(185,'Alexis','Bull','ABULL','650.509.2876','SH_CLERK',4100.00,NULL,121,50,'2014-03-05 00:00:00'),(186,'Julia','Dellinger','JDELLING','650.509.3876','SH_CLERK',3400.00,NULL,121,50,'2014-03-05 00:00:00'),(187,'Anthony','Cabrio','ACABRIO','650.509.4876','SH_CLERK',3000.00,NULL,121,50,'2014-03-05 00:00:00'),(188,'Kelly','Chung','KCHUNG','650.505.1876','SH_CLERK',3800.00,NULL,122,50,'2014-03-05 00:00:00'),(189,'Jennifer','Dilly','JDILLY','650.505.2876','SH_CLERK',3600.00,NULL,122,50,'2014-03-05 00:00:00'),(190,'Timothy','Gates','TGATES','650.505.3876','SH_CLERK',2900.00,NULL,122,50,'2014-03-05 00:00:00'),(191,'Randall','Perkins','RPERKINS','650.505.4876','SH_CLERK',2500.00,NULL,122,50,'2014-03-05 00:00:00'),(192,'Sarah','Bell','SBELL','650.501.1876','SH_CLERK',4000.00,NULL,123,50,'2014-03-05 00:00:00'),(193,'Britney','Everett','BEVERETT','650.501.2876','SH_CLERK',3900.00,NULL,123,50,'2014-03-05 00:00:00'),(194,'Samuel','McCain','SMCCAIN','650.501.3876','SH_CLERK',3200.00,NULL,123,50,'2014-03-05 00:00:00'),(195,'Vance','Jones','VJONES','650.501.4876','SH_CLERK',2800.00,NULL,123,50,'2014-03-05 00:00:00'),(196,'Alana','Walsh','AWALSH','650.507.9811','SH_CLERK',3100.00,NULL,124,50,'2014-03-05 00:00:00'),(197,'Kevin','Feeney','KFEENEY','650.507.9822','SH_CLERK',3000.00,NULL,124,50,'2014-03-05 00:00:00'),(198,'Donald','OConnell','DOCONNEL','650.507.9833','SH_CLERK',2600.00,NULL,124,50,'2014-03-05 00:00:00'),(199,'Douglas','Grant','DGRANT','650.507.9844','SH_CLERK',2600.00,NULL,124,50,'2014-03-05 00:00:00'),(200,'Jennifer','Whalen','JWHALEN','515.123.4444','AD_ASST',4400.00,NULL,101,10,'2016-03-03 00:00:00'),(201,'Michael','Hartstein','MHARTSTE','515.123.5555','MK_MAN',13000.00,NULL,100,20,'2016-03-03 00:00:00'),(202,'Pat','Fay','PFAY','603.123.6666','MK_REP',6000.00,NULL,201,20,'2016-03-03 00:00:00'),(203,'Susan','Mavris','SMAVRIS','515.123.7777','HR_REP',6500.00,NULL,101,40,'2016-03-03 00:00:00'),(204,'Hermann','Baer','HBAER','515.123.8888','PR_REP',10000.00,NULL,101,70,'2016-03-03 00:00:00'),(205,'Shelley','Higgins','SHIGGINS','515.123.8080','AC_MGR',12000.00,NULL,101,110,'2016-03-03 00:00:00'),(206,'William','Gietz','WGIETZ','515.123.8181','AC_ACCOUNT',8300.00,NULL,205,110,'2016-03-03 00:00:00'),(207,'xingxing','zhou','554555@qq.com',NULL,NULL,NULL,NULL,NULL,NULL,NULL),(208,'xiaohu',NULL,'555145@126.com',NULL,NULL,NULL,NULL,NULL,NULL,NULL);/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
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1 length()：获取字节数

说明：我们在MySQL中创建数据库时，有一个操作就是要指定数据库的字符集，而这里的获取字节数的函数——length()就和这个字符集相关的。

在这里简单说一下常见的MySQL字符集一个字符所占用的字节数。(详见文章：MySQL字符集，文章地址：)

utf8(注意：不是utf-8)：数字、字母占用一个字符，常见的中文字符占用3个字节，不能存储占用4个字节的生僻汉字、emoji等。
utf8mb4（真utf-8）：数字、字母占用一个字符，常见的中文字符占用3个字节，但是可以存储占用4个字节的生僻汉字、emoji等。
gbk：数字、字母占用一个字符，常见的中文字符占用2个字节，不能存储占用4个字节的生僻汉字、emoji等。（没想到吧，gbk不能存储中文生僻字）

另外，再说一个命令：SHOW VARIABLES LIKE '%char%' ——查看系统字符集设置，包括所有的字符集设置：（关于这个字符集的说明，详见文章：MySQL字符集，文章地址：）

当前我的数据库是utf8md4字符集，其他的字符集自行测试。

（1）数字、字母、常见中文字符

#运行结果：6
SELECT LENGTH("aaa111")#运行结果：6
SELECT LENGTH("老王")

（2）生僻字

注意：这个生僻字需要从这里拷贝过去（" "），不能直接打出来（不是你用拼音打出来的"康熙"的“熙”，这是一个异体字。另外，本人测试过，这个异体字在知乎上可能会显示不出来，看我的截图就行。）。

#运行结果：4
SELECT LENGTH(" ");

2 concat()

1、函数的使用

由于在MySQL中，"+"只是做加法运算的，因此拼接字符串就不能使用“+”了，需要使用concat()函数。

#错误的写法，不能使用"+"
SELECT last_name+first_name AS "姓名"  FROM employees;#正确的姿势
SELECT CONCAT(last_name,first_name) AS "姓名" FROM employees;

2、使用注意

该函数在进行拼接时，只要拼接的字段有null值，则拼接结果一定为null，必须使用ifnull()函数进行处理！(关于ifnull函数的用法，详见文章：ifnull()，文章地址：)

对null值不进行处理时，拼接结果为null：

#不对null值进行处理
SELECT last_name,first_name,CONCAT(last_name, first_name) AS "姓名" 
FROMemployees ;

对null值进行处理后，可正常拼接

#对null值进行处理
SELECT last_name,first_name,CONCAT(IFNULL(last_name, ""), first_name) AS "姓名" 
FROMemployees ;

3 upper()、lower()

1、该函数的作用

upper()：返回字符串str根据当前字符集映射所有字符为大写。简言之，就是将字符串中所有的字母字符转换为大写

lower()：与上面的upper()相反，转换为小写。

2、使用

【案例1】将姓变为大写，名变为小写，然后进行拼接

#SQLyog使用技巧：F12键可对SQL语句进行格式化排版
SELECT UPPER(last_name) AS '姓',LOWER(first_name) AS '名' ,CONCAT(UPPER(last_name), "_", LOWER(first_name)) AS "姓名" 
FROMemployees ;

4 substr()( 或substring() ）

首先说明一下：MySQL中的下标都是从1开始的。

1、函数作用：截取字符串。该方法有四个重载方法，如下图所示：

2、使用

（1）SUBSTR(str,pos)：截取指定索引pos处后所有的字符串。

【案例1】截取字符串"李莫愁爱上了陆展元"中的"陆展元"

#注意：下标是从1开始的
SELECT SUBSTR("李莫愁爱上了陆展元",7) AS out_put;

（2）SUBSTR(str,pos,len)：从指定索引pos处开始截取字符串str，截取字符长度为len。

【案例1】截取字符串""李莫愁爱上了陆展元"中的"李莫愁"

SELECT SUBSTR("李莫愁爱上了陆展元",1,3) AS out_put;

【案例2】姓名中首字母大写，其他字符小写，然后用_拼接

SELECT last_name,first_name,CONCAT(UPPER(SUBSTR(last_name, 1, 1)),"_",LOWER(SUBSTR(last_name, 2)),"_",LOWER(first_name)) AS out_put 
FROMemployees ;

5 instr()

作用：返回此字符串在指定字符串中第一次出现的索引

#运行结果3
SELECT INSTR("我是张三，我的名字叫张三三","张三") AS result;

6 trim()

作用1：去除前后空格

#运行结果：13
SELECT LENGTH(TRIM("   我是 张三   ")) AS result;

作用2：去除前后指定的字符串

#运行结果：张三bb
SELECT TRIM('a' FROM 'aaaaa张三bbaaa') AS result;

#注意：如果写两个aa，运行结果就是 a张三bba
#两个两个进行匹配，最后还剩下一个a没有被匹配上，所以就留下了
SELECT TRIM('aa' FROM 'aaaaa张三bbaaa') AS result;

7 lpad()

作用：左填充。当字符串长度不足指定的长度时，左填充指定的字符串

注意：如果字符串长度超过指定长度，则会进行左起开始截断！

#运行结果：00100
SELECT LPAD("100",5,"0") AS result;

#字符串长度超长，运行结果：12345
SELECT LPAD("1234567",5,"0") AS result;

8 rpad()

作用：右填充。当字符串长度不足指定的长度时，左填充指定的字符串

注意：如果字符串长度超过指定长度，则会进行左起开始截断！

#运行结果：10000
SELECT RPAD("100",5,"0") AS result;#字符串本身的长度已经超过了指定长度，左起开始截断
#所以运行结果是：10
SELECT RPAD("100",2,"0") AS result;

9 replace()

作用：替换字符串

#运行结果：我是李四，我的名字叫李四三
SELECT REPLACE("我是张三，我的名字叫张三三","张三","李四") AS result;