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mysql切换数据库提醒警示,常见的失实及实施方案

shell> mysql -h hostname -u username -P port -p -A

查阅主库在阴差阳错的附和岗位的施行语句,可透过SQL得出那时候update的呼应的主键值。

中间有关标准,SQL提供了四种相配形式:

 

 

出于MYSQL中数据库太大,导致读取预读时间太长,进而体现那些提醒,即便在此之前都并没有凌驾那个标题,那么暴发那些难题的缘故恐怕是出于有改动数据库信息的操作,比如drop贰个十分大的表(几千万数目)而中途终止.

 

Oracle 10g以上的本子用法为:

Sqlserver  UrlEncode

create table class(
  class_id int,
  class_name varchar(20),
  class_grade char(1)
);

insert into class values (1,'语文','A');
insert into class values (2,'数学','B');
insert into class values (3,'英语','C');

create table score(
  class_id int,
  stu_id varchar(20),
  Score int
);

insert into score values (1,'A001',91);
insert into score values (2,'A001',95);
insert into score values (1,'A002',82);
insert into score values (2,'A002',87);
insert into score values (3,'B003',65);

mysql> use test
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

查询trends_uint表对应主键值的数据行。

再例如 [ ] 内有一多级字符(01234、abcde之类的)则可略写为“0-4”、“a-e”
SELECT * FROM [user] WHERE u_name LIKE '老[1-9]'
将找出“老1”、“老2”、……、“老9”;

if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[UrlEncode]') and xtype in (N'FN', N'IF', N'TF'))
-- 删除函数
drop function [dbo].[UrlEncode]
GO
CREATE FUNCTION dbo.UrlEncode(@URL varchar(3072))
RETURNS varchar(3072)
AS
BEGIN 
 DECLARE @count int,
@char varchar(2),
@i int,
@bytes binary(2),
@low8 int,
@high8 int

DECLARE @URLEncode varchar(3000) ;
SET @count = LEN(@URL)
SET @i = 1
SET @URLEncode = ''
WHILE (@i <= @count)
BEGIN
 SET @char = SUBSTRING(@URL,@i,1)
 IF @char LIKE '[-A-Za-z0-9()''*._!]' AND DATALENGTH(@char) = 1
  SET @URLEncode = @URLEncode + @char
 ELSE
 BEGIN
  IF DATALENGTH(@char) = 1
  BEGIN
   SET @URLEncode = @URLEncode + '%' + SUBSTRING('0123456789ABCDEF',(ASCII(@char) / 16 + 1),1)
   SET @URLEncode = @URLEncode + SUBSTRING('0123456789ABCDEF',(ASCII(@char) % 16 + 1),1)
  END
  ELSE
  BEGIN
   SET @bytes = CONVERT(binary,@char)
   SET @high8 = (0xFF00 & CAST(@bytes AS int))/256
   SET @low8 = 0x00FF & CAST(@bytes AS int)
   SET @URLEncode = @URLEncode + '%' + SUBSTRING('0123456789ABCDEF',(@high8 / 16 + 1),1)
   SET @URLEncode = @URLEncode + SUBSTRING('0123456789ABCDEF',(@high8 % 16 + 1),1)
   SET @URLEncode = @URLEncode + '%' + SUBSTRING('0123456789ABCDEF',(@low8 / 16 + 1),1)
   SET @URLEncode = @URLEncode + SUBSTRING('0123456789ABCDEF',(@low8 % 16 + 1),1)
  END
 END
 SET @i = @i + 1

END
    RETURN @URLEncode;
END

/**********************过滤条件在on中时**********************/
小结一下,如若 left join on leftTable.id=rightTable.id 后还恐怕有别的标准化:
(1)and leftTable.colName='***',过滤左表,不过左表不满意条件的行直接出口,并将右表对应部分置为null
(2)and rightTable.colName='***',过滤右表,对左表未有影响
(3)and leftTable.colName='***' and rightTable.colName='***',就是地点(1)和(2)一同发挥效能

Database changed
mysql> q
Bye
[root@localhost ~]# mysql -u root -p -A
Enter password:
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 12
Server version: 5.7.23 MySQL Community Server (GPL)

 

鉴于通配符的由来,导致大家查询特殊字符“%”、“_”、“[”的口舌无法不奇怪完成,而把特别字符用“[ ]”括起便可不奇怪查询。据此大家写出以下函数:
function sqlencode(str)
str=replace(str,"[","[[]") '此句必须要在最前
str=replace(str,"_","[_]")
str=replace(str,"%","[%]")
sqlencode=str
end function

mysql> select * from class A left join score B on A.class_id=B.class_id and A.class_name='语文';
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |        1 | A001   |    91 |
|        1 | 语文       | A           |        1 | A002   |    82 |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
|        3 | 英语       | C           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
4 rows in set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id and A.class_name='数学';
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        2 | 数学       | B           |        2 | A001   |    95 |
|        2 | 数学       | B           |        2 | A002   |    87 |
|        1 | 语文       | A           |     NULL | NULL   |  NULL |
|        3 | 英语       | C           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
4 rows in set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id and A.class_name='英语';
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        3 | 英语       | C           |        3 | B003   |    65 |
|        1 | 语文       | A           |     NULL | NULL   |  NULL |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
3 rows in set (0.01 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id and A.class_name='体育';
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |     NULL | NULL   |  NULL |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
|        3 | 英语       | C           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
3 rows in set (0.00 sec)

mysql>

Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.

 

例如 SELECT * FROM [user] WHERE u_name LIKE '[张李王]三'
将寻找“张三”、“李三”、“王三”(实际不是“张李王三”);

mysql> select * from class A left join score B on A.class_id=B.class_id;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |        1 | A001   |    91 |
|        2 | 数学       | B           |        2 | A001   |    95 |
|        1 | 语文       | A           |        1 | A002   |    82 |
|        2 | 数学       | B           |        2 | A002   |    87 |
|        3 | 英语       | C           |        3 | B003   |    65 |
+----------+------------+-------------+----------+--------+-------+
5 rows in set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id and 1=1;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |        1 | A001   |    91 |
|        2 | 数学       | B           |        2 | A001   |    95 |
|        1 | 语文       | A           |        1 | A002   |    82 |
|        2 | 数学       | B           |        2 | A002   |    87 |
|        3 | 英语       | C           |        3 | B003   |    65 |
+----------+------------+-------------+----------+--------+-------+
5 rows in set (0.01 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id and 1=0;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |     NULL | NULL   |  NULL |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
|        3 | 英语       | C           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
3 rows in set (0.00 sec)

mysql> select * from class A left join score B on 1=0;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |     NULL | NULL   |  NULL |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
|        3 | 英语       | C           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
3 rows in set (0.00 sec)

mysql> left join的最重要特点是:不管on后面是什么条件,都会返回左表中的所有行!

mysql> kill 16545618;

 

例如 SELECT * FROM [user] WHERE u_name LIKE '[^张李王]三'
将寻找不姓“张”、“李”、“王”的“赵三”、“孙三”等;
再例如 SELECT * FROM [user] WHERE u_name LIKE '老[^1-4]'
将排除“老1”到“老4”,寻找“老5”、“老6”、……、“老9”。

 

mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

 

再比方须求寻觅u_name中既有“三”又有“猫”的记录,请使用and条件
SELECT * FROM [user] WHERE u_name LIKE '%三%' AND u_name LIKE '%猫%'

/**********************过滤条件在where中时**********************/

mysql> show processlist ;    (查看进度)

三、优化建议

1、% :表示狂妄0个或多少个字符。可相配大肆类型和尺寸的字符,有个别景况下假使普通话,请使用七个百分号(%%)表示。

过滤条件写在where中时,先依据where条件对表进行过滤,然后再实行left join

    意思是 预读这一个库中表以及表列音讯,日常原因是当库中表比相当多,表中多少非常大时,就能够并发执行use <库名>后半天没影响,连接极慢的景色,解决办法正是 -A 方式登入数据库,不会预读库中表新闻。

在乎:使用pt工具包首先要设置pt工具包和设置perl模块。

mysql切换数据库提醒警示,常见的失实及实施方案。备注:%三:表示左相配。三%:表示右相称。%三%:表示模糊查询。

不管on前边有啥样原则,left join都要重回左表中的全数行!

(eg:shell> mysql -h 127.0.0.1 -u root -P 3306 -p -A)

2.透彻技术方案

上面 《'》老[^1-4]《'》是要有单引号的!

翻看表中的数码

mysql> use test
Database changed
mysql>

 

select * from flow_user where regexp_like(username, '[张王李]飞')

设若on前边的口径是左表中的列(and leftTable.colName='***'),左表中满足条件的行和右表中的行实行相称(依照on leftTable.id=rightTable.id);左表中不满意条件的行,直接出口,其对应的右表中的列都是null。

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

 

3、[ ] :表示括号内所列字符中的三个(类似正则表明式)。钦定多个字符、字符串或限制,须求所配对象为它们中的任三个。

 

 

 

再例如 SELECT * FROM [user] WHERE u_name LIKE '%三%猫%'
虽说能检索出“三脚猫”,但无法寻觅出符合条件的“张猫三”。

 

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

 

备注
在询问前将待查字符串先经该函数管理就可以,並且在网页上连年数据库用到那类的询问语句时侯要专心:
例如 Select * FROM user Where name LIKE '老[^1-4]'

始建两张表并插入一些数码

删去这几个锁表的情事,小编的mysql就会健康访谈了。

【干货】Linux Shell常用精彩脚本收藏

再例如 SELECT * FROM [user] WHERE u_name LIKE '三__'
只搜索“三脚猫”那样name为八个字且第三个字是“三”的;

mysql> select * from class A left join score B on A.class_id=B.class_id and A.class_name='语文' and B.Score=90;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |     NULL | NULL   |  NULL |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
|        3 | 英语       | C           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
3 rows in set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id and A.class_name='语文' and B.Score=91;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |        1 | A001   |    91 |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
|        3 | 英语       | C           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
3 rows in set (0.01 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id and A.class_name='体育' and B.Score=90;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |     NULL | NULL   |  NULL |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
|        3 | 英语       | C           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
3 rows in set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id and A.class_name='体育' and B.Score=82;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |     NULL | NULL   |  NULL |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
|        3 | 英语       | C           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
3 rows in set (0.00 sec)

mysql>

上海图书馆中锁表的id为16545618,则足以选择kill命令,截止它.

假诺当前高可用架构为Master-Master,则以下均在从库的操作都不可能不set sql_log_bin=0,制止从库施行的言语同步到主库(苏醒时以主库的数目为准)。

例如 SELECT * FROM [user] WHERE u_name LIKE '%三%'
将会把u_name为“张三”,“张猫三”、“三脚猫”,“三藏法师”等等有“三”的记录全寻觅来。

正如上边几组查询结果
--假让你对left join丰富纯熟的话,先不要看结果,是不是足以一贯透露下边查询的结果

本机登陆数据库,直接实践-A也是足以的。

(1)   从库甘休复制

实施数据库查询时,有总体查询和歪曲查询之分。
平日模糊语句格式如下:
SELECT 字段 FROM 表 WHERE 某字段 LIKE 条件

 

图片 1

 

* 表示查找的是全部新闻,举例select * from tbl_user 

mysql> select * from class A left join score B on A.class_id=B.class_id where A.class_name='语文';
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |        1 | A001   |    91 |
|        1 | 语文       | A           |        1 | A002   |    82 |
+----------+------------+-------------+----------+--------+-------+
2 rows in set (0.01 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id where A.class_name='数学';
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        2 | 数学       | B           |        2 | A001   |    95 |
|        2 | 数学       | B           |        2 | A002   |    87 |
+----------+------------+-------------+----------+--------+-------+
2 rows in set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id where A.class_name='英语';
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        3 | 英语       | C           |        3 | B003   |    65 |
+----------+------------+-------------+----------+--------+-------+
1 row in set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id where A.class_name='体育';
Empty set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id where B.Score=90;
Empty set (0.01 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id where B.Score=91;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |        1 | A001   |    91 |
+----------+------------+-------------+----------+--------+-------+
1 row in set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id where A.class_name='语文' and B.Score=90;
Empty set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id where A.class_name='语文' and B.Score=91;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |        1 | A001   |    91 |
+----------+------------+-------------+----------+--------+-------+
1 row in set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id where A.class_name='体育' and B.Score=90;
Empty set (0.00 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id where A.class_name='体育' and B.Score=91;
Empty set (0.00 sec)

mysql> 

Database changed
mysql>

 

例如 SELECT * FROM [user] WHERE u_name LIKE '_三_'
只找出“唐三藏”,这样u_name为两个字且中间二个字是“三”的;

mysql> select * from class;
+----------+------------+-------------+
| class_id | class_name | class_grade |
+----------+------------+-------------+
|        1 | 语文       | A           |
|        2 | 数学       | B           |
|        3 | 英语       | C           |
+----------+------------+-------------+
3 rows in set (0.00 sec)

mysql> select * from score;
+----------+--------+-------+
| class_id | stu_id | Score |
+----------+--------+-------+
|        1 | A001   |    91 |
|        2 | A001   |    95 |
|        1 | A002   |    82 |
|        2 | A002   |    87 |
|        3 | B003   |    65 |
+----------+--------+-------+
5 rows in set (0.00 sec)

mysql>

另一种情况,不也许切换访问数据库,提醒此音讯。(作者没蒙受过,一并贴过来询问下)

 

4、[^ ] :表示不在括号所列之内的单个字符。其取值和 [] 一样,但它要求所配成对象为钦点字符以外的任一个字符。

mysql> select * from class A left join score B on A.class_id=B.class_id and B.Score=90;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        1 | 语文       | A           |     NULL | NULL   |  NULL |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
|        3 | 英语       | C           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
3 rows in set (0.01 sec)

mysql> select * from class A left join score B on A.class_id=B.class_id and B.Score=65;
+----------+------------+-------------+----------+--------+-------+
| class_id | class_name | class_grade | class_id | stu_id | Score |
+----------+------------+-------------+----------+--------+-------+
|        3 | 英语       | C           |        3 | B003   |    65 |
|        1 | 语文       | A           |     NULL | NULL   |  NULL |
|        2 | 数学       | B           |     NULL | NULL   |  NULL |
+----------+------------+-------------+----------+--------+-------+
3 rows in set (0.01 sec)

mysql>

    登陆数据库后,采纳数据库时意识以下提示,

该命令能够查看该表是不是发生多少不均等情形,若有,则使用pt-table-sync修复。

2、_ : 表示大肆单个字符。相称单个放肆字符,它常用来限制表明式的字符长度语句:

 

Enter password:

本着主旨表,能够定制自动数据校验脚本,每一周进行数量校验,但不可能不要在作业低谷实行校验哦!

注:oracle like 不补助正则,你能够行使协助like的正则regexp_like

假如on前面包车型地铁标准是右表中的列(and rightTable.colName='***'),首先会依据(and rightTable.colName='***')过滤掉右表中不满意条件的行;然后,左表中的行依照(on leftTable.id=rightTable.id)和右表中知足条件的行开展相配。

从库:

5、查询内容包罗通配符时

 

如果要找“-”字符请将其放在首个人:'张三[-1-9]';

从库:

在复制由于1045、1032、1062的缘故中断后,应使用三.1的临时应用方案,苏醒复制后再在业务低谷使用pt-check-sum检查数据一致性。

与常见主从复制境遇管理方式一样。

 

 1062:从库插入数据,爆发独一性争执。此时从库已经有同样主键的数码,如果再插入同样主键值的数额则会报错。能够查看主库的改行数据与从库的要插入数据是不是一律,如一致则跳过荒唐,复苏SQL线程,如分化,则以主库为准,将从库的该行记录删除,再打开复制。

依照GTID复制情形

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