MySQL查询展现一而再的结果

作者:数据库

#mysql中 对于查询结果只呈现n条一而再行的难点#

在领扣上遇见的二个难点:求满意条件的连日3行结果的显得

X city built a new stadium, each day many people visit it and the stats are saved as these columns: id, date, people;
Please write a query to display the records which have 3 or more consecutive rows and the amount of people more than 100(inclusive).
For example, the table stadium:
 ------ ------------ ----------- 
| id   | date       | people    |
 ------ ------------ ----------- 
| 1    | 2017-01-01 | 10        |
| 2    | 2017-01-02 | 109       |
| 3    | 2017-01-03 | 150       |
| 4    | 2017-01-04 | 99        |
| 5    | 2017-01-05 | 145       |
| 6    | 2017-01-06 | 1455      |
| 7    | 2017-01-07 | 199       |
| 8    | 2017-01-08 | 188       |
 ------ ------------ ----------- 

For the sample data above, the output is:
 ------ ------------ ----------- 
| id   | date       | people    |
 ------ ------------ ----------- 
| 5    | 2017-01-05 | 145       |
| 6    | 2017-01-06 | 1455      |
| 7    | 2017-01-07 | 199       |
| 8    | 2017-01-08 | 188       |
 ------ ------------ ----------- 

1.先是先举办结果集的查询

select id,date,people from stadium where people>=100;

2.给查询的结果集扩张二个自增列

SELECT @newid:=@newid 1 AS newid,test.* 
FROM(SELECT @newid:=0)r, test WHERE people>100

3.自增列和id的差值 同样即一而再

SELECT @newid:=@newid 1 AS newid,test.* ,@cha:=id-@newid AS cha 
FROM(SELECT @newid:=0)r, test WHERE people>100

4.将一直以来的差值 放在同样张表中,并收取三番五次数量抢先3的

select if(count(id)>=3,count_concat(id),null)e from(
SELECT @newid:=@newid 1 AS newid,test.* ,@cha:=id-@newid AS cha 
FROM(SELECT @newid:=0)r, test WHERE people>100)
as d group by cha

5.将上步获得的表和主表 取得所供给的

SELECT id,DATE,people FROM test,
(SELECT IF (COUNT(id)>3,GROUP_CONCAT(id),NULL)e 
FROM (SELECT @newid:=@newid 1 AS newid,test.* ,@cha:=id-@newid AS cha 
FROM(SELECT @newid:=0)r, test WHERE people>100)AS d   GROUP BY cha ) AS f 
WHERE f.e IS NOT NULL AND FIND_IN_SET(id,f.e);

闻讯还足以用存储进程来实现,可是本人没尝试,稍后尝试

以上

INSERT INTO bookcategory(category_id,category,parent_id) VALUES(1,'计算机',0);//指定插入的顺序


INSERT INTO bookcategory VALUES(1,'计算机',0);//按照默认的插入


INSERT INTO bookcategory(category_id,category,parent_id) VALUES(1,'计算机',0),(2,'xxx',3)(3,'xxxxx',4);//同时插入多条数据


INSERT INTO bookcategory SELECT * FROM test WHERE id>5//将查询结果插入表中


CREATE TABLE TEXT(

    category_id INT PRIMARY KEY AUTO_INCREMENT,

    parent_id INT NOT NULL

)AUTO_INCREMENT=5;    //auto_increment让这一列自动设置编号,默认初始值为,最后为设置初始值为5



ALTER TABLE bookcategory MODIFY category_id INT AUTO_INCREMENT=X//为已有表添加自增列



ALTER TABLE bookcategory MODIFY category_id INT;//去掉自增列


//有外键关系的话添加自增,要先去掉外键关系。


ALTER TABLE bookinfo DROP FOREIGN KEY fk_bcid//去掉外键


ALTER TABLE bookinfo ADD CONSTRAINT fk_bcid FOREIGN KEY(bookcdategory_id) REFERENCES bookcategory(category_id);//添加外键


SELECT price FROM bookinfo WHERE book_id=201501;//查询book_id为201501书的价格


SELECT * FROM readerinfo//查看读者信息表


SELECT xxx,xxx,xxx FROM readerinfo//查询指定列


SELECT xxx,xxx,xxx FROM readerinfo WHERE press='机械工业'//设置外加条件的查询


SELECT DISTINCT press FROM bookinfo;//显示不重复的查询


SELECT * FROM readerinfo WHERE age IS NULL;//查询为空的列


UPDATE readerinfo SET balance =balance -18.9*0.05 WHERE card_id='xxxxxxxx'//更新readerinfo这个表中的card_id为xxx的balance


DELETE FROM readerinfo WHERE card_id='201531513133'//单表数据记录的删除,不加where则为全部删除


TRUNCATE TABLE readerinfo;//删除原表再创建空表


SELECT COUNT(*) FROM readerinfo WHERE sex='男'//对查询结果的分组


SELECT sex FROM readerinfo GROUP BY sex;//查询有多少种性别


SELECT sex COUNT(*) FROM readerinfo GROUP BY sex;//统计每种性别的人数


SELECT sex FROM readerinfo GROUP BY sex WHERE COUNT(sex)>3;//也可以加限制条件。统计每种性别的人数


SELECT     * FROM bookinfo ORDER BY price//对查询结果排序,默认为升序


SELECT     * FROM bookinfo ORDER BY price,store;//price相同的,按照库存排序


SELECT * FROM bookinfo ORDER BY price ASC,store DESC;//asc升序,desc降序


SELECT * FROM bookinfo LIMIT 3;//limit限制查询数量,偏移量为0开始,显示前三行


SELECT * FROM bookinfo LIMIT 2,2;//显示第二条语句的后两个语句


SELECT store,COUNT(*) FROM bookinfo GROUP BY store ORDER BY store DESC LIMIT 4;//统计库存个数,并降序排序,并查看前四条语句

##将SQL再次来到结果作为有的时候表来询问

本文来源:

INSERT INTO bookcategory(category_id,category,parent_id) VALUES(1,'Computer',0);//钦定插入的依次
INSERT INTO bookcategory VALUES(1,'计算机',0);//根据私下认可的插入
INSERT INTO bookcategory(category_id,category,parent_id) VALUES(1,'计算机',0),(2,'xxx',3)(3,'xxxxx',4);//同有时候插入多条数据
INSERT INTO bookcategory SELECT * FROM test WHERE id>5//将查询结果插入表中
CREATE TABLE TEXT(
category_id INT PRIMARY KEY AUTO_INCREMENT,
parent_id INT NOT NULL
)AUTO_INCREMENT=5; //auto_increment让这一列自动安装编号,暗中认可初阶值为,最后为设置开端值为5
ALTER TABLE bookcategory MODIFY category_id INT AUTO_INCREMENT=X//为已有表增添自增列
ALTER TABLE bookcategory MODIFY category_id INT;//去掉自增列
//有外键关系的话加多自增,要先去掉外键关系。
ALTER TABLE bookinfo DROP FOREIGN KEY fk_bcid//去掉外键
ALTER TABLE bookinfo ADD CONSTRAINT fk_bcid FOREIGN KEY(bookcdategory_id) REFERENCES bookcategory(category_id);//增加外键
SELECT price FROM bookinfo WHERE book_id=201501;//查询book_id为二〇一六01书的价格
SELECT * FROM readerinfo//查看读者消息表
SELECT xxx,xxx,xxx FROM readerinfo//查询内定列
SELECT xxx,xxx,xxx FROM readerinfo WHERE press='机械工业'//设置外加条件的询问
SELECT DISTINCT press FROM bookinfo;//呈现不重复的查询
SELECT * FROM readerinfo WHERE age IS NULL;//查询为空的列
UPDATE readerinfo SET balance =balance -18.9*0.05 WHERE card_id='xxxxxxxx'//更新readerinfo这些表中的card_id为xxx的balance
DELETE FROM readerinfo WHERE card_id='二零一六31513133'//单表数据记录的删除,不加where则为任何刨除
TRUNCATE TABLE readerinfo;//删除原表再次创下制空表
SELECT COUNT(*) FROM readerinfo WHERE sex='男'//对查询结果的分组
SELECT sex FROM readerinfo GROUP BY sex;//查询某些许种性别
SELECT sex COUNT(*) FROM readerinfo GROUP BY sex;//总计各类性别的总人口
SELECT sex FROM readerinfo GROUP BY sex WHERE COUNT(sex)>3;//也可以加限制条件。总括每一种性别的食指
SELECT * FROM bookinfo O福睿斯DEQX56 BY price//对查询结果排序,默以为升序
SELECT * FROM bookinfo OOdysseyDE奥德赛 BY price,store;//price一样的,遵照仓库储存排序
SELECT * FROM bookinfo ORDER BY price ASC,store DESC;//asc升序,desc降序
SELECT * FROM bookinfo LIMIT 3;//limit限制查询数量,偏移量为0始发,突显前三行
SELECT * FROM bookinfo LIMIT 2,2;//展现第二条语句的后五个语句
SELECT store,COUNT(*) FROM bookinfo GROUP BY store ORAV4DE冠道 BY store DESC LIMIT 4;//计算仓库储存个数,并降序排序,并查阅前四条语句

测试二:

dbcc checkident('t1',reseed,0)

 

测试一:

参数: table_name:是要对其眼前标记值实行反省的表名。钦点的表必需含有标记列。表名必得相符标志符法规。 NORESEED:内定不应更动当前标志值。 RESEED:内定相应改造当前标志值。 new_reseed_value:用作标记列的脚下值的新值。 WITH NO_INFOMSGS:打消显示全部消息性新闻。

 

 

大家要查询表t1的脚下标记值,sql如下:

 

如何查询三个表中同一字段的例外数据值

语法:

#发卖职员(顾客角色中间表)

DBCC CHECKIDENT (   table_name   [, { NORESEED | { RESEED [,new_reseed_value ] } } ]  )  [ WITH NO_INFOMSGS ]

 

办法一:使用TRUNCATE TABLE语句: TRUNCATE TABLE删除表中的有所行,而不记录单个行删除操作,同有的时候间重新初始化自增列。TRUNCATE TABLE 在效用上与未有WHERE子句的DELETE语句同样;可是,TRUNCATE TABLE 速度更加快,使用的系统财富和事情日志能源更加少。

1
select refid from bbscs_sales_income_stat where type = 4 and month '2012-02' and amount != 0

艺术二:使用DBCC CHECKIDENT语句: DBCC CHECKIDENT在 SQL Server 二零零六 Tucson第22中学反省钦赐表的此时此刻标志值,如有须求,则转移标志值。还是能利用 DBCC CHECKIDENT 为标志列手动设置新的眼下标志值。

表明:左表是数额多的优秀表(基准表如b表)。left join查询。where条件是左侧的不胜表(a表)有些字段(a1)为Null作为(判断字段)

身体力行:大家要重新载入参数表t1的此时此刻标志值为0,sql如下:

-------------结果-------------   
id name id score   
------------------------------   
1 lee 1 90   
2 zhang 2 100  

成都百货上千时候我们需求重新设置有些表的自增列,让自增列重新从1起首记数。最蠢的法门自然是把该表删掉再重新建表了。其实,还会有别的的章程能够重新初始化自增列的值:

(3)那么获取差值

dbcc checkident('t1',noreseed)

1
2
3
select t4.userid fromselect from (select userid from bbscs_role_user where roleid = 'sales') t2 left join 
(select refid from bbscs_sales_income_stat where type = 4 and month '2012-02' and amount != 0) t1 on 
t2.userid = t1.refid WHERE t1.refid is null ) t3, bbscs_org_user t4 where t3.userid = t4.userid order by orgId

 

 

批注:包涵table1的具有子句,根据内定条件再次回到table2相应的字段,不相符的以null展现

#########数据库,以此是SQL语句模型 END############

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##SQL语句,mysql 查询多少个表中分歧的值(首若是差值)  这几个讲话查询依旧存在难题。

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