MySQL一些常用高级SQL语句

MySQL高级SQL语句

use kgc;create table location (Region char(20),store_name char(20));insert into location values ('East','Boston') ;insert into location values ('East','New York');insert into location values ('west','Los Angeles');insert into location values ('west','Houston') ;

---- SELECT ---- 显示表格中一个或数个栏位的所有资料语法: SELECT "栏位" FROM "表名";SELECT Store_Name FROM Store_Info;

---- DISTINCT ---- 不显示重复的资料语法: SELECT DISTINCT "栏位" FROM "表名";SELECT DISTINCT Store_Name FROM Store_Info;

---- WHERE ---- 有条件查询语法:SELECT "栏位” FROM "表名" WHERE "条件";SELECT Store_Name FROM Store_Info WHERE Sales > 1000;

---- AND OR ---- 且 或语法:SELECT "栏位" FROM "表名” WHERE "条件1" {[ANDIOR] "条件2"}+;SELECT Store_Name FROM Store_Info WHERE Sales > 1000 OR (Sales < 500 AND Sales > 200);

---- IN ---- 显示己知的值的资料语法: SELECT "栏位" FROM "表名" WHERE "栏位" IN ('值1','值2', ...);SELECT * FROM Store_Info WHERE Store_Name IN ('Los Angeles','Houston');

---- BETWEEN ---- 显示两个值范围内的资料语法:SELECT "栏位" FROM "表名" WHERE "栏位" BETWEEN '值1' AND '值2';SELECT * FROM Store_Info WHERE Date BETWEEN '2020-12-06' AND '2020-12-10';

---- 通配符 ---- 通常通配符都是跟LIKE一起使用的% : 百分号表示零个、一个或多个字符_ : 下划线表示单个字符'A_Z':所有以‘A'起头，另一个任何值的字符，且以Z'为结尾的字符串。例如，'A.BZ'和‘A.22'都符合这一个模式，而‘AKK2'并不符合(因为在A和Z之间有两个字符，而不是一个字符)。'ABC%':所有以'ABC'起头的字符串。例如，'ABCD'和'ABCABC'都符合这个模式。'%XYZ':所有以'XYZ'结尾的字符串。例如，'WXYZ'和‘ZZXYZ'都符合这个模式。'%AN%':所有含有'AN'这个模式的字符串。例如，'LOS ANGELES'和'SAN FRANCISCO'都符合这个模式。'_AN%':所有第二个字母为‘A'和第三个字母为'N'的字符串。例如，'SAMN FRANCITSCO'符合这个模式，而'LOS ANGELES'则不符合这个模式。---- LIKE ---- 匹配一个模式来找出我们要的资料语法:SELECT "栏位" FROM "表名" WHERE "栏位" LIKE {模式};SELECT * FROM Store_Info WHERE Store_Name like '%os%';---- ORDER BY ---- 按关键字排序语法:SELECT "栏位" FROM "表名" [WHERE "条件"] ORDER BY "栏位" [ASC，DESC];#ASC是按照升序进行排序的,是默认的排序方式。#DESC是按降序方式进行排序。SELECT Store_Name,Sales,Date FROM Store_Info ORDER BY Sales DESC;

abs(x)                #返回x的绝对值rand()                #返回0到1的随机数mod(x,y)              #返回x除以y以后的余数power(x,y)            #返回x的y次方round(x)              #返回离x最近的整数round(x,y)            #保留x的y位小数四舍五入后的值sqrt(x)               #返回x的平方根truncate(x,y)         #返回数字x截断为y位小数的值ceil(×)               #返回大于或等于x的最小整数floor(x)              #返回小于或等于x的最大整数greatest(x1,x2...)    #返回集合中最大的值least(x1,x2...)       #返回集合中最小的值SELECT abs(-1),rand(),mod(5,3),power(2,3),round(1.89);SELECT round(1.8937,3),truncate(1.235,2),ceil(5.2),floor(2.1),least(1.89,3,6.1,2.1);

字符串函数:trim()             #返回去除指定格式的值concat(x,y)        #将提供的参数x和y拼接成一个字符串substr(x,y)        #获取从字符串x中的第y个位置开始的字符串，跟substring()函数作用相同substr(x,y,z)      #获取从字符串x中的第y个位置开始长度为z的字符串length(x)          #返回字符串x的长度replace(x,y,z)     #将字符串z替代字符串x中的字符串yupper(x)           #将字符串x的所有字母变成大写字母lower(x)           #将字符串x的所有字母变成小写字母left(x,y)          #返回字符串x的前y个字符right(x,y)         #返回字符串x的后y个字符repeat(x,y)        #将字符串x重复y次space(x)           #返回x个空格strcmp (x,y)       #比较x和y，返回的值可以为-1,0,1reverse(x)         #将字符串x反转SELECT concat(Region,Store_Name) FROM location WHERE Store_Name = 'Boston';#如sql_mode开启开启了PIPES_AS_CONCAT，"||"视为字符串的连接操作符而非或运算符,和字符串的拼接函数concat相类似，这和Oracle数据库使用方法一样的SELECT Region || ' ' || Store_Name FROM location WHERE Store_Name = 'Boston';SELECT substr(Store_Name,3) FROM location WHERE Store_Name = 'Los Angeles';SELECT substr(Store_Name,2,4) FROM location WHERE Store_Name = 'New York';SELECT TRIM ([ [位置] [要移除的字符串] FROM ] 字符串);#[位置]:的值可以为 LEADING(起头)，TRAILING(结尾)，BOTH(起头及结尾)。#[要移除的字符串]:从字串的起头、结尾，或起头及结尾移除的字符串。缺省时为空格SELECT TRIM(LEADING 'Ne' FROM 'New York');SELECT Region,length(Store_Name) FROM location;SELECT REPLACE(Region,'ast','astern')FROM location;

---- EXISTS ---- 用来测试内查询有没有产生任何结果，类似布尔值是否为真#如果有的话，系统就会执行外查询中的SQL语句。若是没有的话，那整个SQL语句就不会产生任何结果。语法: SELECT "栏位1" FROM "表格1" WHERE EXISTS (SELECT * FROM "表格2" WHERE "条件");SELECT SUM(Sales) FROM Store_Info WHERE EXISTS (SELECT * FROM location WHERE Region = 'West');

在这里插入图片描述

UPDATE Store_Info SET store_name='washington'WHERE sales=300;

在这里插入图片描述

inner join(内连接):只返回两个表中联结字段相等的行left join(左连接):返回包括左表中的所有记录和右表中联结字段相等的记录right join(右连接):返回包括右表中的所有记录和左表中联结字段相等的记录SELECT * FROM location A INNER JOIN Store_Info B on A.Store_Name = B.store_Name ;SELECT * FROM location A RIGHT JOIN Store_Info B on A.Store_Name = B.Store_Name ;SELECT * FROM location A,store_Info B WHERE A.Store_Name = B.Store_Name;SELECT A.Region REGION,SUM(B.Sales) SALES FROM location A,Store_Info BWHERE A.Store_Name = B.Store_Name GROUP BY REGION;

---- CREATE VIEW ---- 视图，可以被当作是虚拟表或存储查询。·视图跟表格的不同是，表格中有实际储存资料，而视图是建立在表格之上的一个架构，它本身并不实际储存资料。·临时表在用户退出或同数据库的连接断开后就自动消失了，而视图不会消失。·视图不含有数据，只存储它的定义，它的用途一般可以简化复杂的查询。比如你要对几个表进行连接查询，而且还要进行统计排序等操作，写SQT语句会很麻烦的，用视图将几个表联结起来，然后对这个视图进行查询操作，就和对一个表查询一样，很方便。语法:CREATE VIEW "视图表名” AS "SELECT语句";CREATE VIEW V_REGION_SALES AS SELECT A.Region REGION, SUM(B.Sales) SALES FROM location AINNER JOIN Store_Info B ON A.Store_Name = B.Store_Name GROUP BY REGION;SELECT * FROM V_REGION_SALES;DROP VIEW V_REGION_SALES;

---- UNION ---- 联集，将两个SQL语句的结果合并起来，两个SQI语句所产生的栏位需要是同样的资料种类UNION:生成结果的资料值将没有重复，且按照字段的顺序进行排序语法:[SELECT 语句 1] UNION [SELECT 语句2];UNION ALL:将生成结果的资料值都列出来，无论有无重复语法:[SELECT 语句 1] UNION ALL [SELECT 语句 2];SELECT Store_Name FROM location UNION SELECT Store_Name FROM Store_Info;SELECT Store_Name FROM location UNION ALL SELECT Store_Name FROM Store_Info;

----- 交集值 ---- 取两个SQL语句结果的交集SELECT A.Store_Name FROM location A INNER JOIN Store_Info B ON A.Store_Name = B.Store_Name;SELECT A.Store_Name FROM location A INNER JOIN Store_Info B USING(Store_Name);#两表基中的一个表没有指定的行，而另一个表这个行有重复，并且确实有交集的时候用SELECT A.Store_Name FROM(SELECT Store_Name FROM location UNION ALL SELECT Store_Name FROM store_Info) AGROUP BY A.Store_Name HAVING COUNT(*) > 1;#取两个sQL语句结果的交集,且没有重复SELECT A.Store_Name FRONM (SELECT B.Store_Name FROM location B INNER JOIN Store_Info C ON B.Store_Name = C.store_Name) AGROUP BY A.Store_Name;SELECT DISTINCT A.Store_Name FROM location A INNER JOIN Store_Info B USING(Store_Name);SELECT DISTIMCT Store_Name FROM location WHERE (Store_Name) IN (SELECT Store_Name FROM Store_Info);SELECT DISTINCT A.Store_Name FROM location A LEFT JOIN Store_Info B USING(Store_Name) WHERE B.Store_Name IS NOT NULL;

---- 无交集值 ---- 显示第一个sQL语句的结果，且与第二个SQL语句没有交集的结果，且没有重复SELECT DISTINCT Store_Name FROM location WHERE (Store_Name) NOT IN (SELECT Store_Name FROM Store_Info);SELECT DISTINCT A.Store_Name FROM location A LEFT JOIN Store_Info B USING(Store_Name) WHERE B.Store_Name IS NULL;

---- CASE ---- 是 SQL 用来做为 IF-THEN-ELSE 之类逻辑的关键字语法:SELECT CASE ("栏位名")  WHEN "条件1” THEN "结果1"  WHEN "条件2" THEN "结果2"  ...  [ELSE "结果N"]  ENDFROM "表名";#"条件"可以是一个数值或是公式。ELSE子句则并不是必须的。SELECT store_Name, CASE Store_Name  WHEN 'Los Angeles' THEN Sales * 2  WHEN 'Boston' THEN Sales * 1.5  ELSE Sales  END"New Sales",DateFROM Store_Info;#"New Sales"是用于CASE 那个栏位的栏位名。CREATE TABLE Total_Sales (Name char(10),sales int(5));INSERT INTO Total_Sales VALUES ('zhangsan',10);INSERT INTO Total_Sales VALUES ('lisi',15);INSERT INTO Total_Sales VALUES ('wangwu',20);INSERT INTO Total_Sales VALUES ('zhaoliu',40);INSERT INTO Total_Sales VALUES ('sunqi',50);INSERT INTO Total_Sales VALUES ('zhouba',20);INSERT INTO Total_Sales VALUES ('wujiu',30);

----算排名----表格自我连结(Self Join)，然后将结果依序列出，算出每一行之前〈包含那一行本身)有多少行数SELECT A1.Name, A1.sales,COUNT(A2.sales) Rank FROM Total_sales A1,Total_sales A2WHERE A1.sales < A2.sales 0R (A1.sales = A2.sales AND A1.Name = A2.Name)GROUP BY A1.Name, A1.sales ORDER BY A1.sales DESC;例如：select A1.Name,A1.sales,count(A2.sales) rank from Total_Sales A1,Total_Sales A2 where A1.sales <  A2.sales OR (A1.sales=A2.sales and A1.Name=A2.Name) group by A1.Name order by A1.sales desc;解释：当A1的sales字段值小于A2的sales字段值、或者两表sales字段值相等并且Name字段值相等时，从A1和A2表中查询A1的Name字段值、A1的sales字段值、和A2的sales字段的非空值rank是别名，并为A1的Name字段分组，A1的sales字段降序排序

---- 算中位数 ----SELECT Sales Middle FROM (SELECT A1.Name,A1.Sales,COUNT(A2.Sales) Rank FROM Total_Sales A1,Total_Sales A2WHERE A1.Sales < A2.Sales 0R (A1.Sales = A2.Sales AND A1.Name >= A2.Name)GROUP BY A1.Name,A1.Sales ORDER BY A1.Sales DESC) A3WHERE A3.Rank = (SELECT (COUNT(*)+1) DIV 2 FROM Total_Sales);例如：select * from (select A1.Name,A1.sales,count(A2.sales) rank from Total_Sales A1,Total_Sales A2 where A1.sales < A2.sales OR (A1.sales=A2.sales and A1.Name=A2.Name) group by A1.Name order by A1.sales desc) A3 where A3.rank = (select (count(*)+1) DIV 2 from Total_Sales);select sales mid from (select A1.Name,A1.sales,count(A2.sales) rank from Total_Sales A1,Total_Sales A2 where A1.sales < A2.sales OR (A1.sales=A2.sales and A1.Name=A2.Name) group by A1.Name order by A1.sales desc) A3 where A3.rank = (select (count(*)+1) DIV 2 from Total_Sales);#每个派生表必须有自己的别名，所以别名A3必须要有#DIV 是在MySQL中算出商的方式

---- 算累积总计 ---- 表格自我连结(Self Join)，然后将结果依序列出,算出每一行之前(包含那一行本身)的总合SELECT A1.Name, A1.Sales, SUM(A2.Sales) Sum_Total FROM Total_Sales A1，Total_Sales A2WHERE A1.Sales < A2.Sales OR (A1.Sales=A2.Sales AND A1.Name = A2.Name)GROUP BY A1.Name,A1.Sales ORDER BY A1.Sales DESC;例如：select A1.*,sum(A2.sales) sum_soales from Total_Sales A1,Total_Sales A2 where A1.sales < A2.sales or(A1.sales=A2.sales and A1.Name=A2.Name) group by A1.Name order by A1.sales desc;

例如：select A1.*,A1.sales/(select sum(sales) from Total_Sales) z_sum from Total_Sales A1,Total_Sales A2 where A1.sales < A2.sales or (A1.sales=A2.sales and A1.Name=A2.Name) group by A1.Name;#select sum(sales) from Total_Sales 是为了算出字段值总合，然后每一行一一除以总合，算出每行的总合百分比。

例如：select A1.Name,A1.sales,sum(A2.sales),sum(A2.sales)/(select sum(sales) from Total_Sales) Z from Total_Sales A1,Total_Sales A2 where A1.sales < A2.sales or (A1.sales=A2.sales and A1.Name=A2.Name) group by A1.Name order by A1.sales desc;select A1.Name,A1.sales,sum(A2.sales),TRUNCATE(sum(A2.sales)/(select sum(sales) from Total_Sales),2) ||'%' Z from Total_Sales A1,Total_Sales A2 where A1.sales < A2.sales or (A1.sales=A2.sales and A1.Name=A2.Name) group by A1.Name order by A1.sales desc;

1、无值的长度为0，不占用空间；而空值null 的长度是null，是占用空间的
2、IS NULL或者IS NOT NULL，是用来判断字段是不是NULL或者不是NULL，是不能查出是不是无值的
3、无值的判断使用='‘或者<>''来处理。<>代表不等于
4、在通过count()指定字段统计又多少行数时，如果遇到NULL值会自动忽略掉，遇到空值会自动加入记录中进行计算

例如：create table SITE(site varchar(20));insert into SITE values('nanjing');insert into SITE values('beijing');insert into SITE values('');insert into SITE values('taijin');insert into SITE values();insert into SITE values('');select * from SITE;

匹配模式描述实例^ 匹配文本的开始字符 ‘^bd' 匹配以 bd 开头的字符串$ 匹配文本的结束字符 ‘qn$' 匹配以 qn 结尾的字符串. 匹配任何单个字符‘s.t' 匹配任何 s 和 t 之间有一个字符的字符串* 匹配零个或多个在它前面的字符 ‘fo*t' 匹配 t 前面有任意个 o+ 匹配前面的字符 1 次或多次‘hom+' 匹配以 ho 开头，后面至少一个m 的字符串字符串 匹配包含指定的字符串 ‘clo' 匹配含有 clo 的字符串p1|p2 匹配 p1 或 p2 ‘bg|fg' 匹配 bg 或者 fg[...] 匹配字符集合中的任意一个字符 ‘[abc]' 匹配 a 或者 b 或者 c[^...] 匹配不在括号中的任何字符 ‘[^ab]' 匹配不包含 a 或者 b 的字符串{n} 匹配前面的字符串 n 次 ‘g{2}' 匹配含有 2 个 g 的字符串{n,m}匹配前面的字符串至少 n 次，至多m 次‘f{1,3}' 匹配 f 最少 1 次，最多 3 次

例如：select * from Total_Sales where Name regexp '^[n]';select * from Total_Sales where Name regexp '[n]';select * from Total_Sales where Name regexp 'Ho|Bo';

存储过程在使用过程中是将常用或者复杂的工作预先使用SQL语句写好并用一个指定的名称来进行储存，这个过程经编译和优化后存储在数据库服务器中，当需要使用该存储过程时，只需要调用它即可，存储过程在执行上比传统SQL速度更快，执行效率更高。

存储过程的优点
1、执行一次后，会将生成的二进制代码驻留缓冲区，提高执行效率
2、SQL语句加上控制语句的集合，灵活性高
3、在服务器端存储，客户端调用时，降低网络负载
4、可多次重复被调用，可随时修改，不影响客户端调用
5、可完成所有的数据库操作，也可控制数据库的信息访问权限

语法：DELIMITER !!    #将语句的结束符号从分号；临时修改，以防出问题，可以自定义CREATE PROCEDURE XXX()  #创建存储过程，过程名自定义,（）可带参数 BEGIN       #过程体以关键字BEGIN开始 select * from xxx;  #过程体语句 END!!    #过程体以关键字END结尾DELIMITER ;     #将语句的结束符号恢复为分号call XXX;  #调用存储过程====查看存储过程====show create procedure [数据库.]储存过程名;   #查看某个储存过程的具体信息show create procedure XXX;show procedure status [like '%XXX%'] \G

例如：DELIMITER !!CREATE PROCEDURE KIND7(IN num int(10))BEGINdeclare var int;set var=num*2;if var>=10 thenupdate Total_Sales set sales=sales+1;else update Total_Sales set sales=sales-1;end if;END!!DELIMITER ;CALL KIND7(5);CALL KIND7(4);

例如：create table akg(id int);DELIMITER !!CREATE PROCEDURE KIND6()BEGINdeclare var int;set var=0;while var<5 doinsert into akg values(var);set var=var+1;end while;END!!DELIMITER ;CALL KIND6;select * from akg;

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