mysql left join查询,相比较三个表分化行

3.自增列和id的差值 相同即连续,2.给查询的结果集增加一个自增列,INSERT INTO bookcategory VALUES(1,INSERT INTO bookcategory(category,A表中的字段a有40000条数据,而不仅仅是联接列所匹配的行,使用TRUNCATE TABLE语句,还有其它的方法可以重置自增列的值

#mysql中 对于查询结果只体现n条一而再行的主题材料#

在领扣上超越的三个难点:求餍足条件的连天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.第风度翩翩先进行结果集的询问

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 相通即连续

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

4.将相似的差值 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.将上步获得的表和主表 拿到所急需的

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);

听讲还能用存款和储蓄进程来成功,然则作者没尝试,稍后尝试

以上

 

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

参数:
table_name:是要对其前段时间标记值实行检查的表名。钦赐的表必得带有标志列。表名必需符合标志符法则。
NORESEED:钦赐不应改正当前标记值。 RESEED:钦命相应改变当前标记值。
new_reseed_value:用作标志列的方今值的新值。 WITH
NO_INFOMSGS:打消突显全数消息性音讯。

 

 # —>22条记录

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

 

 

亲自过问:咱们要重新苏醒设置表t1的一时一刻标记值为0,sql如下:

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
1
2
3
4
5
6
7
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';

正文来源:

INSERT INTO bookcategory(category_id,category,parent_id)
VALUES(1,’Computer’,0);//钦点插入的相继
INSERT INTO bookcategory VALUES(1,’Computer’,0);//依照暗中同意的插入
INSERT INTO bookcategory(category_id,category,parent_id)
VALUES(1,’Computer’,0),(2,’xxx’,3)(3,’xxxxx’,4);//相同的时候插入多条数据
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,暗中认可开头值为,最终为设置初叶值为5
ALTER TABLE bookcategory MODIFY category_id INT
AUTO_INCREMENT=X//为已有表加多自增列
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);//加多外键
SELECT price FROM bookinfo WHERE
book_id=201501;//查询book_id为二零一五01书的价钱
SELECT * FROM readerinfo//查看读者信息表
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;//呈现不另行的询问
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那些表中的card_id为xxx的balance
DELETE FROM readerinfo WHERE
card_id=’201631513133’//单表数据记录的删除,不加where则为任何删减
TRUNCATE TABLE readerinfo;//删除原表再次创下立空表
SELECT COUNT(*) FROM readerinfo WHERE sex=’男’//对查询结果的分组
SELECT sex FROM readerinfo GROUP BY sex;//查询有稍许种性别
SELECT sex COUNT(*) FROM readerinfo GROUP BY sex;//总计每一种性别的人数
SELECT sex FROM readerinfo GROUP BY sex WHERE
COUNT(sex)>3;//也得以加节制规范。计算各类性其余人口
SELECT * FROM bookinfo O大切诺基DE奇骏 BY price//对查询结果排序,默以为升序
SELECT * FROM bookinfo OLANDDELacrosse BY
price,store;//price相近的,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起始,显示前三行
SELECT * FROM bookinfo LIMIT 2,2;//展现第二条语句的后多少个语句
SELECT store,COUNT(*) FROM bookinfo GROUP BY store O中华VDE福特Explorer 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

id score
1 90
2 100

大家要询问表t1的一时一刻标记值,sql如下:

 

措施二:使用DBCC CHECKIDENT语句: DBCC CHECKIDENT在 SQL Server 贰零壹零 安德拉2中检查钦定表的脚下标记值,如有需要,则修改标志值。还足以选择 DBCC
CHECKIDENT 为标志列手动设置新的如今标志值。

table2

dbcc checkident(‘t1’,noreseed)

1
2
select t1.Userid from bbscs_role_user t1 left join bbscs_sales_income_stat t2 on t1.userid = t2.refid 
and t1.roleid = 'sales' and t2.type = 4 and t2.month '2012-02' and t2.amount != 0 and t2.id is null

格局黄金时代: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,同一时候重新设置自增列。TRUNCATE
TABLE 在固守上与未有WHERE子句的DELETE语句相像;但是,TRUNCATE TABLE
速度越来越快,使用的系统能源和事情日志能源越来越少。

例如:

成都百货上千时候大家供给重新设置有个别表的自增列,让自增列重新从1发端记数。最蠢的办法自然是把该表删掉再重新建表了。其实,还会有其它的主意能够重新设置自增列的值:

4 wang null null   
——————————  

dbcc checkident(‘t1’,reseed,0)

 

语法:

##跟顾客单位中间表关联,按部门id排序显示。

A表中的字段a有40000条数据
B表中的字段a有60000条数据,当中的40000条数据跟A表是风姿洒脱致的
怎么着能把那差异等的二〇〇一0条数据查询出来呀?

#总结表(客商出卖记录表卡塔 尔(英语:State of Qatar)

###越发有力的临时表查询效用,将上述查询结果作为贰个完整放入。

3 steve
4 wang

 

##where or and 区别