MySQL查询展现接二连三的结果

#mysql中 对于查询结果只体现n条三番五次行的题目#

在领扣上碰见的多个主题素材:求知足条件的接二连三3行结果的来得

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.给查询的结果集扩大多个自增列

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 相同即三番五次

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

4.将长期以来的差值 放在同等张表中,并抽出一而再数量超过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.将上步得到的表和主表 取得所急需的

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);

听他们说仍然是能够用存款和储蓄进度来完结,可是本身没尝试,稍后尝试

以上

 

什么查询四个表中同一字段的不等数据值

好多时候大家要求重新设置某些表的自增列,让自增列重新从1开端记数。最蠢的不二等秘书籍自然是把该表删掉再另行建表了。其实,还也有任何的法子可以重新初始化自增列的值:

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

例如:

办法大器晚成:使用TRUNCATE TABLE语句: TRUNCATE
TABLE删除表中的具备行,而不记录单个行删除操作,同一时候重新恢复设置自增列。TRUNCATE
TABLE 在效劳上与从不WHERE子句的DELETE语句相似;然则,TRUNCATE TABLE
速度越来越快,使用的系统能源和职业日志能源更加少。

 

A表中的字段a有40000条数据
B表中的字段a有60000条数据,在那之中的40000条数据跟A表是如出风度翩翩辙的
什么能把那不等同的二〇〇二0条数据查询出来呀?

方式二:使用DBCC CHECKIDENT语句: DBCC CHECKIDENT在 SQL Server 2009 路虎极光2中检查内定表的眼下标志值,如有须求,则转移标志值。还是可以选拔 DBCC
CHECKIDENT 为标记列手动设置新的脚下标志值。

 

 

语法:

INSERT INTO bookcategory(category_id,category,parent_id)
VALUES(1,’Computer’,0);//钦定插入的依次
INSERT INTO bookcategory VALUES(1,’Computer’,0);//依据暗许的插入
INSERT INTO bookcategory(category_id,category,parent_id)
VALUES(1,’Computer’,0),(2,’xxx’,3)(3,’xxxxx’,4);//同期插入多条数据
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,暗中认可起头值为,最后为设置早先值为5
ALTER TABLE bookcategory MODIFY category_id INT
AUTO_INCREMENT=X//为本来就有表加多自增列
ALTER TABLE bookcategory MODIFY category_id INT;//去掉自增列
//有外键关系的话增加自增,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);//增加外键
SELECT price FROM bookinfo WHERE
book_id=201501;//查询book_id为201601书的价格
SELECT * FROM readerinfo//查看读者音信表
SELECT xxx,xxx,xxx FROM readerinfo//查询钦定列
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;//突显不另行的查询
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这么些表中的card_id为xxx的balance
DELETE FROM readerinfo WHERE
card_id=’二〇一五31513133’//单表数据记录的去除,不加where则为总体去除
澳门新萄京,TRUNCATE TABLE readerinfo;//删除原表再成立空表
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;//计算每一种性其别人头
SELECT sex FROM readerinfo GROUP BY sex WHERE
COUNT(sex)>3;//也足以加约束规范。总括每一种性其他食指
SELECT * FROM bookinfo OLANDDE奥迪Q5 BY price//对查询结果排序,默以为升序
SELECT * FROM bookinfo O奇骏DE福睿斯 BY
price,store;//price雷同的,依照仓库储存排序
SELECT * FROM bookinfo ORDER BY price ASC,store
DESC;//asc升序,desc降序
SELECT * FROM bookinfo LIMIT
3;//limit节制查询数量,偏移量为0发轫,呈现前三行
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 O牧马人DEEscort BY store DESC
LIMIT 4;//总计仓库储存个数,并降序排序,并查阅前四条语句

–建表table1,table2:   

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

1
2
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8
9
create   table   table1(id   int,name   varchar(10));   
create   table   table2(id   int,score   int);   
insert   into   table1   select   '1','lee';
insert   into   table1   select   '2','zhang';
insert   into   table1   select   '3','steve';
insert   into   table1   select   '4','wang';   
insert   into   table2   select   '1','90';   
insert   into   table2   select   '2','100';   
insert   into   table2   select   '3','70';

参数:
table_name:是要对其方今标记值进行反省的表名。钦定的表必须带有标志列。表名必需切合标志符准绳。
NORESEED:钦定不应校正当前标志值。 RESEED:钦赐相应改换当前标记值。
new_reseed_value:用作标记列的脚下值的新值。 WITH
NO_INFOMSGS:撤消突显全数新闻性音信。

 

亲自过问:大家要重新设置表t1的当前标记值为0,sql如下:

如表
————————————————-   
table1    
————————————————-   
id name  
1 lee
2 zhang

dbcc checkident(‘t1’,reseed,0)

3 steve
4 wang

笔者们要询问表t1的近些日子标志值,sql如下:

————————————————-  

dbcc checkident(‘t1’,noreseed)

table2

正文来源:

————————————————- 

id score
1 90
2 100

3 70

————————————————- 

 

(1)左向外过渡的结果集包罗   left  
outer   子句中钦点的左表的持有行,而不止是联接列所相称的行。假如左表的某行在右表中并未有相配行,则在相关联的结果集行中右表的兼具采取列表列均为空值(null)。  

(2)sql语句  

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