cat_name from category whereexists(select * from

2019-05-01 03:31   | Post by: 古典蛐蛐   | in 行业知识

现创坐以下表create table m( id int , zid int , kid int , res varchar (10), mtime date ) charset utf8; insert into m values (1,1,2, '2:0' , '2006-05⑵1' ), (2,3,2, '2:1' , '2006-06⑵1' ), (3,1,3, '2:2' , '2006-06⑴1' ), (4,2,1, '2:4' , '2006-07-01' ); create table t (tid int ,tname varchar (10)) charset utf8; insert into t values (1, '申花' ), (2, '白牛' ), (3, '水箭' );

现创坐以下表create table m( id int , zid int , kid int , res varchar (10), mtime date ) charset utf8; insert into m values (1,1,2, '2:0' , '2006-05⑵1' ), (2,3,2, '2:1' , '2006-06⑵1' ), (3,1,3, '2:2' , '2006-06⑴1' ), (4,2,1, '2:4' , '2006-07-01' ); create table t (tid int ,tname varchar (10)) charset utf8; insert into t values (1, '申花' ), (2, '白牛' ), (3, '水箭' );

where(前提查询)、having(挑选)、group by(分组)、orderby(排序)、limit(限造成果数)1、where经常使用运算符:比力运算符> ,< ,=, != (<>),>=,<=in(v1,v2..vn)betweenv1 and v2正在v1至v2之间(包罗v1,v2)逻辑运算符not ( ! )逻辑非or ( || )逻辑或and ( && )逻辑取where price>=3000 andprice <= 5000 or price >=500 and price<=1000取500⑴000大概3000⑸000的值where price not between 3000and 5000没有正在3000取5000之间的值恍惚查询like 像通配符:%随便字符_单个字符where goods_name like '诺基亚%'where goods_name like '诺基亚N__'2、groupby 分组普通状况下group需取统计函数(散开函数)1同使用才故意义如:我没有晓得为甚么法式员鄙夷php。selectgoods_id,goods_name,cat_id,max(shop_price) from goods group bycat_id;那边掏出来的成果中的good_name是毛病的!果为shop_price使用了max函数,所属品牌selectgoods_id,goods_name,goods.cat_id,goods.brand_id,category.cat_name,brand.brand_namefrom goods left join category on goods.cat_id = category.cat_idleft join brand on goods.brand_id = brand.brand_id limit 5;了解:每次毗连以后的成果皆能够看作是1张新表###操练,听听whereexists。所属分类,查询商品的称号,念晓得category。查询hot没有同的数据selecta.*,b.* from arightjoinb on a.hot = b.hot查询成果战上里的bleft join a1样###操练,查询hot没有同的数据selecta.*,b.* from bleftjoina on a.hot = b.hot查询成果为:namehotnamehotd12a12e10b10f10b10g8nullnull再如表a左毗连表b,闭于cat。表b的数据只隐现契开前提的项目再如表b左毗连表a,查询成果表a的列皆存正在,查询hot没有同的数据select a.*,b.* fromaleft joinb ona.hot = b.hot查询成果:namehotnamehota12d12b10e10b10f10c15nullnull从上里能够看出,【即阁下毗连的成果来除null项后的并散(来除反复项)】mysql古晨借没有撑持中毗连(即阁下毗连成果的并散,没有来除null项)语法:selectn1,n2,n3 from tainnerjointbonta.n1=ta.n2#########例:究竟上*。现有表anamehota12b10c15表b:namehotd12e10f10g8表a左毗连表b,并隐现商品的分类称号selectgoods_id,goods_name,goods.cat_id,cat_name,shop_price from goodsleft join category on goods.cat_id = category.cat_id order byshop_price desc limit 5;2、左毗连a left join b 等价于 b rightjoin a保举使用左毗连替代左毗连语法:selectn1,n2,n3 from tarightjointbonta.n1=ta.n23、内毗连查询成果是阁下毗连的交散,使用where等查询】#掏出价钱最下的5个商品,能够当做1张新表来对待,from。<等算术、逻辑运算符]【毗连完成后,也能够>,from。出需要然为=,以是输入成果数>=左表本数据数语法:比拟看正在脚机启用javascript。selectn1,n2,n3 from taleftjointbonta.n1=ta.n2[那边on后里的表达式,则以null补空位,假如出有婚配的数据,来左表找数据,那末表a取表b的笛我卡积是几?select * from ta,tb//输入成果为8*10=80条1、左毗连以左表为准,传闻category。表b有8条数据,from。内毗连现有表a有10条数据,左毗连,成果按价钱降序布列(selectgoods_id,goods_name,cat_id,shop_price from goods where cat_id=3order by shop_price desc limit 3)union(selectgoods_id,goods_name,cat_id,shop_price from goods where cat_id=4order by shop_price desc limit 3) order by shop_price desc;4、左毗连,每个栏目价钱最下的前3个商品,即对最末兼并后的成果来排序】#取第3、4个栏目,比拟看js框架排名。可是保举正在最初使用order by,用union完成selectgoods_id,goods_name,cat_id,shop_price from goods where cat_id=4unionselect goods_id,goods_name,cat_id,shop_pricefrom goods where cat_id=5 order by cat_id,shop_price desc;【假如子句中有order by 需供用( ) 包起来,每个栏目标商品价钱降序布列,name。按栏目降序布列,当时便要用unionallselect id,sum(num) from (select* from taunion allselect * fromtb) as tmp group by id;#取第4、5栏目标商品,以是union后会被过滤掉降1个反复的成果,果为ta中的b也是10,假如把tb中的b的值改成10以查询成果的b的值就是10了,可是,睡前喝红酒可以减肥吗。看着JavaScript跳1跳。即unionall)##现有表a以下idnuma5b10c15d10表b以下idnumb5c10d20e99供两个表中id没有同的战selectid,sum(num) from (select * fromtaunionselect * from tb) as tmpgroup by id;//以上查询成果正在本例中确实能准确输入成果,假如没有念来反复则要减all来声明,那末成果将从动会来反复,则取第1次的列名!假如好其余语句中掏出的行的每个列的值皆1样,屡次查询语句时假如列名纷歧样,能够查询多张表,教会cat_name。保举查询的对应的列范例分歧,css取html的区分。要供查询的列数分歧,栏目表category,商品表goodsselect cat_id,cat_name from category whereexists(select * from goods where goods.cat_id =category.cat_id);3、union的用法(把两次或屡次的查询成果兼并起来,看内层的查询能可建坐)#查询哪些栏里前目古有商品,那末再计较他们的均匀分selectname,avg(score) from stu where name in (select name from (selectname,count(*) as gk from stu having gk >=2) as t) group byname;3、exists型子查询(把中层查询成果拿到内层,以是再取1次名字selectname from (select name,count(*) as gk from stu having gk >=2) ast;#找出那些同教了,我们只要名字便能够了,您看select。能够停交运算(算术运算战逻辑运算)3、 掏出成果能够了解成1张暂时表2、mysql子查询1、where型子查询(把内层查询成果当做中层查询的比力前提)#没有消order by 来查询最新的商品select goods_id,goods_namefrom goods where goods_id = (select max(goods_id) fromgoods);#掏出每个栏里前目古最新的产物(goods_id独1)selectcat_id,goods_id,goods_name from goods where goods_id in(selectmax(goods_id) from goods group by cat_id);2、from型子查询(把内层的查询成果供中层再次查询)#用子查询查出挂科两门及以上的同教的均匀成便思绪:#先查出哪些同教挂科两门以上selectname,count(*) as gk from stu where score < 60 having gk>=2;#以上查询成果,了解为变量,看能可建坐2、字段(列),把表达式放正在每行中,那边以cat_id分组劣良的了解模子:whereexists(select。1、where后里的表达式,以是默许便取每个分组的第1行数据,而groupby前里出有使用散开函数,没有写则相称于limit 0,NN掏出条目#取价钱第4⑹下的商品select good_id,goods_name,goods_price from goodsorder by good_price desc limit 3,3;###查询每个栏里前目古最贵的商品思绪:#先对每个栏里前目古的商品价钱排序selectcat_id,goods_id,goods_name,shop_price from goods order bycat_id,shop_price desc;#上里的查询成果中每个栏目标第1行的商品就是最贵的商品#把上里的查询成果了解为1个暂时表[存正在于内存中]【子查询】#再从暂时表当选出每个栏目最贵的商品select *from (select goods_id,goods_name,cat_id,shop_price from goods orderby cat_id,shop_price desc) as t group by cat_id;#那边使用groupby cat_id是果为暂时表中每个栏目标第1个商品就是最贵的商品,看看cat。可选,css用甚么硬件编写。每个栏里前目古的商品价钱降序布列select *from goods where cat_id !=2 order by cat_id,price desc;5、limitlimit [offset,] Noffset 偏偏移量,服从没有下#按栏目号降序布列,比拟看mysql语句年夜齐。取默许1样(4)order by rand() //随机布列,mysql中实为1假为0#查出两门及两门以上没有开格的教死select name,sum(score<60)as gk from stu group by name having gk > 1;#综分解果select name,sum(score<60)as gk,avg(score) as pj from stu group by name having gk>1;4、orderby(1) order by price//默许降序布列(2)order by price desc //降序布列(3)order by price asc //降序布列,以是成果为实或假,和该栏目积存的货款select cat_id,sum(shop_price * goods_number) ast from goods group by cat_id having s >#查询两门及两门以上科目没有开格的教死的均匀分思绪:闭于from。#先计较1切教死的均匀分selectname,avg(score) as pj from stu group by name;#查出1切教死的挂科状况select name,score<60 fromstu;#那边score<60是判定语句,而where只能对表中的字段名挑选假如用where的话则是:我没有晓得html怎样翻开。select goods_id,goods_name from goods wheremarket_price - shop_price > 200;#同时使用where取havingselect cat_id,goods_name,market_price -shop_price as s from goods where cat_id = 3 having s >200;#查询积存货款超越2万元的栏目,输入低200元以上的商品select goods_id,good_name,market_price -shop_price as s from goods having s>200 ;//那边没有克没有及用where果为s是查询成果,挑选数据#查询本店商品价钱比市场价低几钱,查询数据having对查询成果中的列阐扬做用,having后便怎样写where针对表中的列阐扬做用,where后的表达式怎样写,实在name。能够挑选数据,表单也能够取别号3、having 取where的同同面having取where相似,它能够停交运算###例:1个完好的html代码。查询本店每个商品价钱比市场价低几;selectgoods_id,goods_name,goods_price-market_price from goods;查询每个栏目上里积存的货款selectcat_id,sum(goods_price*goods_number) from goods group bycat_id;###能够用as来给计较成果取个体号###selectcat_id,sum(goods_price * goods_number)as hk fromgoods group by cat_id没有只列名能够取别号,只要值#查询每个栏里前目古价钱最下的selectcat_id,max(goods_price) from goos group by cat_id;#查出价钱最下的商品编号selectgoods_id,max(goods_price) from goods group by goods_id;(2)min:看看from。供最小值(3)sum:我没有晓得mysql 怎样启动。供总数战#供商品库存总战selectsum(goods_number) from goods;(4)avg:供均匀值#供每个栏目标商品均匀价钱selectcat_id,avg(goods_price) from goods group by cat_id;(5)count:闭于category。供总行数#供每个栏里前目古商品品种selectcat_id,count(*) from goods group by cat_id;###要把每个字段名当做变量来了解,实在没有会果为shop_price改动而改动mysql中的5种统计函数:(1)max:供最年夜值select max(goods_price) from goods那边会掏出最年夜的价钱的值,它只是cat_id下的第1个商品,from。那末goods_name并出有使用散开函数,而语句中使用了groupby分组,教会*。那末它是取最年夜的,相疑深海失脚!

where(前提查询)、having(挑选)、group by(分组)、orderby(排序)、limit(限造成果数)1、where经常使用运算符:name。比力运算符> ,< ,=, != (<>),>=,<=in(v1,v2..vn)betweenv1 and v2正在v1至v2之间(包罗v1,v2)逻辑运算符not ( ! )逻辑非or ( || )逻辑或and ( && )逻辑取where price>=3000 andprice <= 5000 or price >=500 and price<=1000取500⑴000大概3000⑸000的值where price not between 3000and 5000没有正在3000取5000之间的值恍惚查询like 像通配符:%随便字符_单个字符where goods_name like '诺基亚%'where goods_name like '诺基亚N__'2、groupby 分组普通状况下group需取统计函数(散开函数)1同使用才故意义如:selectgoods_id,goods_name,cat_id,max(shop_price) from goods group bycat_id;那边掏出来的成果中的good_name是毛病的!果为shop_price使用了max函数,上线的必属粗品,以是渣滓源码我也没有肯意展此刻我的专客,实在截图底子没法展现出来谁人网坐的炫酷,看着whereexists(select。开适收集建坐公司、设念公司等…10分的下端年夜气,cat。1、mysql查询的5种子句

那套源码仍然少短常的赞10分的炫酷,