mysql窗口函数

刺骨的言语ヽ痛彻心扉 2023-09-25 09:17 30阅读 0赞

## PHP编程，MYSQL的sum()函数问题，如何打印到页面 ##

$zzhichu=$conn->query("selectsum(money)astotal\_moneyfromrecordwhereusernameid='$usernameid'");

$result=mysql\_fetch\_assoc($zzhichu);

echo$result\['total\_money'\];希望能够帮助你，望采纳，O(∩\_∩)O谢谢

![mysql窗口函数\_mysql窗口函数][mysql_mysql]

## mysql怎么分析函数row ##

select(@i:=@i+1) asi,table\_name.\*fromtable\_name,(select@i:=0)as itset @rownum=0;select @rownum:=@rownum+1 as rownum, t.username from auth\_user t limit 1,5;一直以来，MySQL 只有针对聚合函数的汇总类功能，比如MAX, AVG 等，没有从 SQL 层针对聚合类每组展开处理的功能。不过 MySQL 开放了 UDF 接口，可以用 C 来自己写UDF，这个就增加了功能行难度。这种针对每组展开处理的功能就叫窗口函数，有的数据库叫分析函数。在 MySQL 8.0 之前，我们想要得到这样的结果，就得用以下几种方法来实现：1. session 变量2. group\_concat 函数组合3. 自己写 store routines接下来我们用经典的 学生/课程/成绩 来做窗口函数演示mysql> show create table student \\G\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* 1. row \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*Table: studentCreate Table: CREATE TABLE student ( sid int(10) unsigned NOT NULL, sname varchar(64) DEFAULT NULL, PRIMARY KEY (sid)) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4\_0900\_ai\_ci1 row in set (0.00 sec)mysql> show create table course\\G\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* 1. row \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*Table: courseCreate Table: CREATE TABLE \`course\` ( \`cid\` int(10) unsigned NOT NULL, \`cname\` varchar(64) DEFAULT NULL, PRIMARY KEY (\`cid\`)) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4\_0900\_ai\_ci1 row in set (0.00 sec)mysql> show create table score\\G\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* 1. row \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*Table: scoreCreate Table: CREATE TABLE \`score\` ( \`sid\` int(10) unsigned NOT NULL, \`cid\` int(10) unsigned NOT NULL, \`score\` tinyint(3) unsigned DEFAULT NULL, PRIMARY KEY (\`sid\`,\`cid\`)) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4\_0900\_ai\_ci1 row in set (0.00 sec)mysql> select \* from student;+-----------+--------------+| sid| sname|+-----------+--------------+| 201910001 | 张三|| 201910002 | 李四|| 201910003 | 武松|| 201910004 | 潘金莲|| 201910005 | 菠菜|| 201910006 | 杨发财|| 201910007 | 欧阳修|| 201910008 | 郭靖|| 201910009 | 黄蓉|| 201910010 | 东方不败|+-----------+--------------+10 rows in set (0.00 sec)mysql> select \* from score;;+-----------+----------+-------+| sid| cid| score |+-----------+----------+-------+| 201910001 | 20192001 |50 || 201910001 | 20192002 |88 || 201910001 | 20192003 |54 || 201910001 | 20192004 |43 || 201910001 | 20192005 |89 || 201910002 | 20192001 |79 || 201910002 | 20192002 |97 || 201910002 | 20192003 |82 || 201910002 | 20192004 |85 || 201910002 | 20192005 |80 || 201910003 | 20192001 |48 || 201910003 | 20192002 |98 || 201910003 | 20192003 |47 || 201910003 | 20192004 |41 || 201910003 | 20192005 |34 || 201910004 | 20192001 |81 || 201910004 | 20192002 |69 || 201910004 | 20192003 |67 || 201910004 | 20192004 |99 || 201910004 | 20192005 |61 || 201910005 | 20192001 |40 || 201910005 | 20192002 |52 || 201910005 | 20192003 |39 || 201910005 | 20192004 |74 || 201910005 | 20192005 |86 || 201910006 | 20192001 |42 || 201910006 | 20192002 |52 || 201910006 | 20192003 |36 || 201910006 | 20192004 |58 || 201910006 | 20192005 |84 || 201910007 | 20192001 |79 || 201910007 | 20192002 |43 || 201910007 | 20192003 |79 || 201910007 | 20192004 |98 || 201910007 | 20192005 |88 || 201910008 | 20192001 |45 || 201910008 | 20192002 |65 || 201910008 | 20192003 |90 || 201910008 | 20192004 |89 || 201910008 | 20192005 |74 || 201910009 | 20192001 |73 || 201910009 | 20192002 |42 || 201910009 | 20192003 |95 || 201910009 | 20192004 |46 || 201910009 | 20192005 |45 || 201910010 | 20192001 |58 || 201910010 | 20192002 |52 || 201910010 | 20192003 |55 || 201910010 | 20192004 |87 || 201910010 | 20192005 |36 |+-----------+----------+-------+50 rows in set (0.00 sec)mysql> select \* from course;+----------+------------+| cid| cname|+----------+------------+| 20192001 | mysql|| 20192002 | oracle|| 20192003 | postgresql || 20192004 | mongodb|| 20192005 | dble|+----------+------------+5 rows in set (0.00 sec)MySQL 8.0 之前比如我们求成绩排名前三的学生排名，我来举个用 session 变量和 group\_concat 函数来分别实现的例子：session 变量方式每组开始赋一个初始值序号和初始分组字段。b.cname,a.sname,c.score, c.ranking\_scorestudent a,course b,@cid = c.cid,@rn := @rn + 1,@rn := 1) AS ranking\_score,@cid := c.cid AS tmpcidORDER BY cid,score DESC@rn := 0 rn,@cid := '') initialize\_tableWHERE a.sid = c.sidAND b.cid = c.cidAND c.ranking\_score <= 3ORDER BY b.cname,c.ranking\_score;+------------+-----------+-------+---------------+| cname| sname| score | ranking\_score |+------------+-----------+-------+---------------+| dble| 张三|89 |1 || dble| 欧阳修|88 |2 || dble| 菠菜|86 |3 || mongodb| 潘金莲|99 |1 || mongodb| 欧阳修|98 |2 || mongodb| 郭靖|89 |3 || mysql| 李四|100 |1 || mysql| 潘金莲|81 |2 || mysql| 欧阳修|79 |3 || oracle| 武松|98 |1 || oracle| 李四|97 |2 || oracle| 张三|88 |3 || postgresql | 黄蓉|95 |1 || postgresql | 郭靖|90 |2 || postgresql | 李四|82 |3 |+------------+-----------+-------+---------------+15 rows in set, 5 warnings (0.01 sec)group\_concat 函数方式利用 findinset 内置函数来返回下标作为序号使用。b.cname,a.sname,c.score,FIND\_IN\_SET(c.score, d.gp) score\_rankingstudent a,course b,score c,GROUP\_CONCAT(ORDER BY score DESC SEPARATOR ','GROUP BY cidORDER BY score DESCWHERE a.sid = c.sidAND b.cid = c.cidAND c.cid = d.cidORDER BY d.cid,score\_rankingWHERE score\_ranking <= 3；+------------+-----------+-------+---------------+| cname| sname| score | score\_ranking |+------------+-----------+-------+---------------+| dble| 张三|89 |1 || dble| 欧阳修|88 |2 || dble| 菠菜|86 |3 || mongodb| 潘金莲|99 |1 || mongodb| 欧阳修|98 |2 || mongodb| 郭靖|89 |3 || mysql| 李四|100 |1 || mysql| 潘金莲|81 |2 || mysql| 欧阳修|79 |3 || oracle| 武松|98 |1 || oracle| 李四|97 |2 || oracle| 张三|88 |3 || postgresql | 黄蓉|95 |1 || postgresql | 郭靖|90 |2 || postgresql | 李四|82 |3 |+------------+-----------+-------+---------------+15 rows in set (0.00 sec)MySQL 8.0 窗口函数MySQL 8.0 后提供了原生的窗口函数支持，语法和大多数数据库一样，比如还是之前的例子：用 row\_number() over () 直接来检索排名。b.cname,a.sname,c.score,row\_number() over (PARTITION BY b.cnameORDER BY c.score DESC) score\_rankstudent AS a,course AS b,score AS cWHERE a.sid = c.sidAND b.cid = c.cidWHERE score\_rank <= 3;+------------+-----------+-------+------------+| cname| sname| score | score\_rank |+------------+-----------+-------+------------+| dble| 张三|89 |1 || dble| 欧阳修|88 |2 || dble| 菠菜|86 |3 || mongodb| 潘金莲|99 |1 || mongodb| 欧阳修|98 |2 || mongodb| 郭靖|89 |3 || mysql| 李四|100 |1 || mysql| 潘金莲|81 |2 || mysql| 欧阳修|79 |3 || oracle| 武松|98 |1 || oracle| 李四|97 |2 || oracle| 张三|88 |3 || postgresql | 黄蓉|95 |1 || postgresql | 郭靖|90 |2 || postgresql | 李四|82 |3 |+------------+-----------+-------+------------+15 rows in set (0.00 sec)那我们再找出课程 MySQL 和 DBLE 里不及格的倒数前两名学生名单。b.cname,a.sname,c.score,row\_number () over (PARTITION BY b.cidORDER BY c.score ASC) score\_rankingstudent AS a,course AS b,score AS cWHERE a.sid = c.sidAND b.cid = c.cidAND b.cid IN (20192005, 20192001)AND c.score < 60WHERE score\_ranking < 3;+-------+--------------+-------+---------------+| cname | sname| score | score\_ranking |+-------+--------------+-------+---------------+| mysql | 菠菜|40 |1 || mysql | 杨发财|42 |2 || dble | 武松|34 |1 || dble | 东方不败|36 |2 |+-------+--------------+-------+---------------+4 rows in set (0.00 sec)到此为止，我们只是演示了row\_number() over() 函数的使用方法，其他的函数有兴趣的朋友可以自己体验体验，方法都差不多。

## mysql自定义函数如何传入中文参？mysql自定义函数如何传入 ##

CREATEFUNCTION\`fristPinyin\`(P\_NAMEVARCHAR(255))RETURNSvarchar(255)CHARSETutf8BEGINDECLAREV\_RETURNVARCHAR(255);SETV\_RETURN=ELT(INTERVAL(CONV(HEX(left(CONVERT(P\_NAMEUSINGgbk),1)),16,10),0xB0A1,0xB0C5,0xB2C1,0xB4EE,0xB6EA,0xB7A2,0xB8C1,0xB9FE,0xBBF7,0xBFA6,0xC0AC,0xC2E8,0xC4C3,0xC5B6,0xC5BE,0xC6DA,0xC8BB,0xC8F6,0xCBFA,0xCDDA,0xCEF4,0xD1B9,0xD4D1),'A','B','C','D','E','F','G','H','J','K','L','M','N','O','P','Q','R','S','T','W','X','Y','Z');RETURNV\_RETURN;ENDpinyin：此函数是将一个中文字符串对应拼音母的每个相连(例如："中国人"->ZGR)复制代码代码如下:CREATEFUNCTION\`pinyin\`(P\_NAMEVARCHAR(255))RETURNSvarchar(255)CHARSETutf8BEGINDECLAREV\_COMPAREVARCHAR(255);DECLAREV\_RETURNVARCHAR(255);DECLAREIINT;SETI=1;SETV\_RETURN='';whileIselectp。

![mysql窗口函数\_mysql窗口函数\_02][mysql_mysql_02]

## MySQL截取字符串函数方法有哪些呢？ ##

函数：

1、从左开始截取字符串

left(str, length)

说明：left(被截取字段，截取长度)

例：select left(content,200) as abstract from my\_content\_t

2、从右开始截取字符串

right(str, length)

说明：right(被截取字段，截取长度)

例：select right(content,200) as abstract from my\_content\_t

3、截取字符串

substring(str, pos)

substring(str, pos, length)

说明：substring(被截取字段，从第几位开始截取)

substring(被截取字段，从第几位开始截取，截取长度)

例：select substring(content,5) as abstract from my\_content\_t

select substring(content,5,200) as abstract from my\_content\_t

(注：如果位数是负数 如-5 则是从后倒数位数，到字符串结束或截取的长度)

4、按关键字截取字符串

substring\_index(str,delim,count)

说明：substring\_index(被截取字段，关键字，关键字出现的次数)

例：select substring\_index(”blog。

## mysql的函数使用 ##

SELECT CODE,NAME,其他字段

FROM \`area\`

order by name desc

limit 1,1;select中的if函数是if(a=b,0,other)

if a=b then 0;

else 1;

end if;

![mysql窗口函数\_mysql窗口函数\_03][mysql_mysql_03]

## 什么叫窗口函数 ##

使用窗口函数，您可以通过计算每行周围窗口上的集合值来分析数据。结果集会返回表示一组行的摘要值。您可以使用窗口函数计算一家公司在一段指定时间内的销售数据的移动平均值。

除 LIST 以外的任何集合函数都可以与窗口函数联合使用。

下面的示例显示了一个窗口函数。查询返回一个结果集，该结果集按部门划分数据，然后提供员工薪水的累计汇总(从在公司的时间最长的员工开始)。结果集只包括居住在加利福尼亚、犹他州、纽约或亚利桑那州的那些雇员。Sum Salary 列提供了雇员薪水的累计总额。

SELECT dept\_id, emp\_lname, start\_date, salary,

SUM(salary) OVER (PARTITION BY dept\_id

ORDER BY start\_date

RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS "Sum\_Salary"

FROM employee

WHERE state IN ('CA', 'UT', 'NY', 'AZ') AND dept\_id IN ('100', '200')

ORDER BY dept\_id, start\_date;下面的表是查询的结果集。结果集按部门划分。

对于部门 100，来自加利福尼亚、犹他州、纽约或亚利桑那州的雇员的薪水累计总额是 $434,091.69，而部门 200 的雇员的薪水累计总额是 $250,200.00。

[mysql_mysql]: https://img2.baidu.com/it/u=242391498,841886773&fm=26&fmt=auto
[mysql_mysql_02]: https://img0.baidu.com/it/u=4270988345,1474233368&fm=26&fmt=auto
[mysql_mysql_03]: https://img1.baidu.com/it/u=2223814036,3557195394&fm=26&fmt=auto