A表中的字段a有40000条数据,3金沙js娱乐场官方网站.自增列和id的差值 相同即连续

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,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

#mysql中 对于查询结果只浮现n条连续行的主题材料#

在领扣上遇到的三个标题:求满意条件的连年3行结果的展现

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.先是先举行结果集的询问

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

2.给查询的结果集增添二个自增列

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 同样即三回九转

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,并抽取一连数量超越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 猎取所急需的

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);

闻讯还能够用存款和储蓄进程来实现,可是小编没尝试,稍后尝试

以上

 

 

主意一:使用TRUNCATE TABLE语句: TRUNCATE
TABLE删除表中的有着行,而不记录单个行删除操作,同期重新初始化自增列。TRUNCATE
TABLE 在遵守上与未有WHERE子句的DELETE语句同样;可是,TRUNCATE TABLE
速度越来越快,使用的系统财富和职业日志能源更加少。

(1)左向外对接的结果集包涵   left  
outer   子句中内定的左表的持有行,而不仅有是联接列所相配的行。借使左表的某行在右表中从不相称行,则在相关联的结果集行中右表的装有采用列表列均为空值(null)。  

 

3 steve
4 wang

小编们要查询表t1的当前标志值,sql如下:

##跟客商部门中间表关联,按机关id排序显示。

INSERT INTO bookcategory(category_id,category,parent_id)
VALUES(1,’计算机’,0);//钦定插入的顺序
INSERT INTO bookcategory VALUES(1,’计算机’,0);//依据默许的插入
INSERT INTO bookcategory(category_id,category,parent_id)
VALUES(1,’Computer’,0),(2,’xxx’,3)(3,’xxxxx’,4);//同不常间插入多条数据
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,暗中同意开端值为,最后为设置起首值为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为二〇一四01书的标价
SELECT * FROM readerinfo//查看读者消息表
SELECT xxx,xxx,xxx FROM readerinfo//查询钦命列
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;//彰显不另行的查询
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这一个表中的card_id为xxx的balance
DELETE FROM readerinfo WHERE
card_id=’二零一五31513133’//单表数据记录的去除,不加where则为全方位剔除
TRUNCATE TABLE readerinfo;//删除原表再创立空表
SELECT COUNT(*) FROM readerinfo WHERE sex=’男’//对查询结果的分组
SELECT sex FROM readerinfo GROUP BY sex;//查询有多少种性别
SELECT sex COUNT(*) FROM readerinfo GROUP BY sex;//总括各个性其他食指
SELECT sex FROM readerinfo GROUP BY sex WHERE
COUNT(sex)>3;//也得以加限制标准。总计各个性别的食指
SELECT * FROM bookinfo O福特ExplorerDELacrosse BY price//对查询结果排序,暗许为升序
SELECT * FROM bookinfo OEvoqueDETiggo BY
price,store;//price一样的,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限制查询数量,偏移量为0发轫,展现前三行
SELECT * FROM bookinfo LIMIT 2,2;//突显第二条语句的后四个语句
SELECT store,COUNT(*) FROM bookinfo GROUP BY store O安德拉DE智跑 BY store DESC
LIMIT 4;//总括库存个数,并降序排序,并查看前四条语句

 

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

证实:左表是多少多的不行表(基准表如b表)。left
join查询。where条件是侧边的可怜表(a表)有些字段(a1)为Null作为(推断字段)

 

id score
1 90
2 100

语法:

 

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
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

示范:大家要重新初始化表t1的眼下标志值为0,sql如下:

 

 ##表与表,条件与标准独立出来。

主意二:使用DBCC CHECKIDENT语句: DBCC CHECKIDENT在 SQL Server 二〇〇九 Enclave第22中学反省钦赐表的脚下标志值,如有须要,则转移标记值。还可以选用 DBCC
CHECKIDENT 为标记列手动设置新的此时此刻标记值。

A表中的字段a有50000条数据
B表中的字段a有六千0条数据,在那之中的50000条数据跟A表是同等的
何以能把那差别等的三千0条数据查询出来啊?

4 wang null null   
——————————  

dbcc checkident(‘t1’,reseed,0)

 

证实:左表是多少多的极其表(基准表如b表)。left
join查询。where条件是右侧的格外表(a表)某些字段(a1)为Null作为(剖断字段)

本文来源:

table2

(1)左向外对接的结果集满含   left  
outer   子句中钦命的左表的兼具行,而不只有是联接列所相配的行。假若左表的某行在右表中尚无匹配行,则在相关联的结果集行中右表的全部选拔列表列均为空值(null)。  

众多时候大家须要重新恢复设置某些表的自增列,让自增列重新从1初叶记数。最蠢的法子自然是把该表删掉再重复建表了。其实,还会有其余的办法能够重新恢复设置自增列的值:

id score
1 90
2 100

 

参数:
table_name:是要对其近期标志值举行检讨的表名。钦点的表必需带有标志列。表名必需符合标识符准则。
NORESEED:钦命不应更换当前标志值。 RESEED:内定相应改造当前标志值。
new_reseed_value:用作标志列的当下值的新值。 WITH
NO_INFOMSGS:撤废突显全部消息性音信。

3 steve 3 70
4 wang null null   
——————————  

 

dbcc checkident(‘t1’,noreseed)

 

 

 # —>7条记录

(3)那么获取差值

#销售职员(客户剧中人物中间表)

 

 

 

##将SQL重临结果作为有的时候表来询问