环境mysql 8.0.x 主从gtid: off问题和分析mysql从库延迟太大, SQL线程和IO线程都是Running的, 但延迟有5天左右....SQL线程状态为:applying batch of row changes (delete)图片解析相关relay log得到正在执行的事务信息mysqlbinlog -vvv --base64-output...=decode-row relay.xxxxx --start-position | more查找该表信息, 发现该表无主键, 无索引, 有20+GB, 接近2亿行....图片解决办法跳过该事务后, 观察延迟正在下降
报错和问题分析 报错日志: Cause: java.sql.SQLException: Row 133 was cut by GROUP_CONCAT() ......Cause: java.sql.SQLException: Row 133 was cut by GROUP_CONCAT()\n; uncategorized SQLException; SQL state...[HY000]; error code [1260]; Row 133 was cut by GROUP_CONCAT(); 通过报错日志可以看到是使用GROUP_CONCAT函数报错,查找原因发现是拼接的字符串过长导致无法返回结果...通过查找资料是由于group_concat_max_len参数设置导致的。...Windows 更改my.ini配置文件,添加如下行,扩大允许的拼接字符串最大长度: group_concat_max_len=102400 配置完成后,进入服务,选择MySQL服务,重新启动。
现象 MySQL在删除一张表时出现 ERROR 1217 (23000): Cannot delete or update a parent row: a foreign key constraint...fails 原因 可能是在Mysql中,删除的表和另一张表设置了foreign key的关联,造成无法更新或删除数据; 解决方案 可以通过设置FOREIGN_KEY_CHECKS变量来避免这种情况。
\\\\\\\\\\n"; DELETE删除语句 sql语法: DELETE FROM table_name [WHERE Clause] 如果没有指定 WHERE 子句,MySQL表中的所有记录将被删除...value GROUP BY column_name; GROUP BY 语句根据一个或多个列对结果集进行分组。...演示代码 //需求:使用 GROUP BY 语句 将数据表按名字进行分组,并统计每个人有多少条记录: mysql> SELECT name, COUNT(*) FROM employee_tbl...GROUP BY name; +--------+----------+ | name | COUNT(*) | +--------+----------+ | 小丽 | 1 | |..."Count: {$row['runoob_count']} ".
参数修改持久化 MySQL 8.0版本支持在线修改全局参数并持久化,通过加上PERSIST关键字,可以将修改的参数持久化到新的配置文件(mysqld-auto.cnf)中,重启MySQL时,可以从该配置文件获取到最新的配置参数...5.7 mysql> select count(id), group_own from tb1 group by group_own; +-----------+-----------+ | count...2 | 5 | +-----------+-----------+ 3 rows in set (0.00 sec) # MySQL 8.0.11 mysql> select count...(id), group_own from tb1 group by group_own; +-----------+-----------+ | count(id) | group_own | +---...8.0.11显式地加上order by进行排序 mysql> select count(id), group_own from tb1 group by group_own order by group_own
DELETE 语句 DELETE FROM runoob_tbl WHERE runoob_id=3; MySQL LIKE 子句 相当于模糊匹配 SQL LIKE 子句中使用百分号(%)字符来表示任意字符...GROUP BY 语句 SELECT name, COUNT(*) FROM employee_tbl GROUP BY name;//COUNT(*)是新的字段 使用WITH ROLLUP...例如我们将以上的数据表按名字进行分组,再统计每个人登录的次数: SELECT name, SUM(singin) as singin_count FROM employee_tbl GROUP BY...FROM employee_tbl GROUP BY name WITH ROLLUP; Mysql 连接的使用 接下来我们就使用MySQL的INNER JOIN(也可以省略 INNER...i; MySQL 中使用 ADD 子句来向数据表中添加列,如下实例在表 testalter_tbl 中添加 i 字段,并定义数据类型: ALTER TABLE testalter_tbl ADD
参考: https://sakthismysqlblog.wordpress.com/2020/04/05/mysql-query-rewritten-plugin-now-supporting-delete-insert-update-replace..., INSERT, REPLACE, UPDATE, and DELETE....+ 1'); mysql> SELECT * FROM query_rewrite.rewrite_rules\G *************************** 1. row *******...GROUP BY phone_no ORDER BY amountSum DESC LIMIT 10', 'SELECT DISTINCT phone_no,COUNT(phone_no) phoneNoCount...and ( 1 row in set (0.00 sec) [test]> SELECT DISTINCT phone_no, COUNT(phone_no) phoneNoCount
Mysql修改数据——update 标准 修改 语句 UPDATE 表名 SET 字段名1 = 值1 [ , 字段名2= 值2, …. ] [ WHERE 条件]; Mysql...是整表清除; delete需要执行n(数据记录的条数)次,并产生n条日志记录 truncate只要执行一次;只产生一条日志记录; ③运行速度:drop>truncate>delete ②应用范围:TRUNCATE...table_name [ as table_ alias ] [ left|right|inner join table_name2 ] #联合查询 [ WHERE … ] [ GROUP...BY …] [ HAVING …] [ ORDER BY… ] [ LIMIT { [ offset,] row_count | row_count OFFSET offset...}] ; #指定查询的记录从哪条至哪条 [] 括号代表可选的; {} 括号代表必须的; # MySQL语句中的注释符,也可以用 /该处为注释/
在这一篇,我们将介绍在MySQL 8.0.23中添加的增强功能,从服务器可以获知复制源的成员身份变化(复制源使用组复制)。...当managed_type为“ GroupReplication”时,managed_name将为group_replication_group_name系统变量的值。...如下图3所示,添加了一个具有SOURCE_UUID:37d345fs-341d-66hf-5f54-2345e247680的新源S4,并使用异步复制通道C2将其与其余源连接。 ?...这些增强功能将通过自动添加和删除潜在资源的过程来帮助提高MySQL系统的可用性,并简化维护。...希望您会喜欢此功能的这些增强功能,并希望这种自动化可以改善并简化系统设置并减少错误,从而提供更高的容错能力和更好的系统可用性。
from hwb a where a.id in (select min(id) FROM hwb a group by name having count(name) > 1)...FROM hwb b GROUP BY NAME HAVING count( NAME ) > 1 ) t) AND id NOT IN (select tt.id from (SELECT max(...c.id ) as id FROM hwb c GROUP BY NAME HAVING count( NAME ) > 1 ) tt) 3、实现方法二: 根据name分组,查找出id最小的,然后再查找...count( NAME ) > 1 ) AND id NOT IN (SELECT max(c.id ) as id FROM hwb c GROUP BY NAME HAVING count( NAME...,只需删除一次 delete from hwb WHERE NAME IN (SELECT NAME FROM hwb b GROUP BY NAME HAVING count(NAME) > 1)
概述 今天主要介绍一下Oracle、MySQL、sqlserver、pg数据库在删除重复数据时是怎么实现的。这里用实例来说明。...from hwb a where a.id in (select min(id) FROM hwb a group by name having count(name) > 1)...count( NAME ) > 1 ) AND id NOT IN (SELECT max(c.id ) as id FROM hwb c GROUP BY NAME HAVING count( NAME...where 、group by、 order by 的执行 DELETE FROM hwb a WHERE id IN ( SELECT b.id FROM (SELECT id, ROW_NUMBER...,只需删除一次 delete from hwb WHERE NAME IN (SELECT NAME FROM hwb b GROUP BY NAME HAVING count(NAME) > 1)
BY 分组数据 SELECT age, COUNT(*) FROM example_table GROUP BY age; -- 14、使用 HAVING 进一步筛选分组数据 SELECT age,...COUNT(*) FROM example_table GROUP BY age HAVING COUNT(*) > 1; -- 15、使用子查询 SELECT * FROM example_table...计算关联表中的记录数 SELECT a.id, COUNT(b.id) as count FROM table1 a LEFT JOIN table2 b ON a.id = b.id GROUP...= 0; SELECT (@row_number:=@row_number+1) AS row_num, name FROM example_table; -- 44、显示当前数据库中的所有表...SHOW TABLES; -- 45、使用SHOW VARIABLES查看 MySQL 的配置变量: SHOW VARIABLES LIKE 'version%'; -- 46、创建临时表并插入数据
主键: 表中每一行都应该有可以唯一标识自己的一列,用于记录两条记录不能重复,任意两行都不具有相同的主键值 ---- ---- MySQL 数据操作 DML 更改字段属性 alter table..., 'lamp138' ); Query OK, 1 row affected ( 0.11 sec) -- 不指定 字段添加值 mysql> insert into...-- 可以使用分组进行统计,更方便 select sex, count (*) from users group by sex; +------+----------+...(*) from users group by classid; +---------+----------+ | classid | count (*) | +--...可以给不同的用户,或者项目,创建不同的 mysql 用户,并适当的授权,完成数据库的相关操作 这样就一定程度上保证了数据库的安全。
),sum(age) from user; 二、 group by 分组 主体结构 select count(字段) from 表名 group by 字段 统计 男生和女生分别有多少人 select...sex,count(*) from user group by sex; 统计每班有多少人 select class,count(*) from user group by class; 统计 每班的男生和女生分别有多少人...select class,sex,count(*) as count from user group by class,sex; having 分组的条件的使用 相当于 where 查询人数大于2人的班级...select class,count(*) as count from user group by class having count>2; 查询班级为 3班和4班的人数 select class,...select class,count(*) as count from user group by class having class in('onlin3','onlin4') and count
in set (0.00 sec) mysql> delete from exam_result where name='孙悟空'; Query OK, 1 row affected (0.01 sec...1 row in set (0.00 sec) 2 统计收集的 qq 号有多少 -- NULL 不会计入结果 mysql> select count(qq) from exam_result; +---...-- COUNT(math) 统计的是全部成绩 mysql> select count(math) from exam_result; +-------------+ | count(math) |...mysql> select count(distinct math) from exam_result; +----------------------+ | count(distinct math)...by配合使用,对group by结果进行过滤 mysql> select deptno,avg(sal) deptavg from emp group by deptno having deptavg
触发器(trigger):监视某种情况,并触发某种操作,它是提供给程序员和数据分析员来保证数据完整性的一种方法,它是与表事件相关的特殊的存储过程,它的执行不是由程序调用,也不是手工启动,而是由事件来触发...失败; DELIMITER $ create trigger tri_delete_blocks_infos1 before delete on blocks_infos for each row begin...blocks from blocks_infos where infos_id=new.infos_id group by infos_id; end $ DELIMITER ; 注意关于MySQL...的触发器: DELIMITER $ CREATE TRIGGER tri_delete_blocks_infos after DELETE ON blocks_infos FOR EACH ROW BEGIN...DELIMITER $ create trigger tri_delete_blocks_infos1 before delete on blocks_infos for each row begin
自己封装的Mysql简易操作类,已塞在Ben框架中,基于PDO来写的,代码风格上有些无厘头。。。 mysql.class.php <?...; if($re){ return true; }else{ return false; } } public function DELETE...=null){ $sql = "DELETE FROM ".$table." WHERE ".$Conditionsname."='"....."';"; }else{ $sql = "DELETE FROM ".$table."...; if($re){ return true; }else{ return false; } } public function group
; +----------+ | count(*) | +----------+ | 10000 | +----------+ 1 row in set (0.007 sec) [testdb] ...> select (user_id%4) as hash_id,count(*) FROM gravity_t1 group by (user_id%4); +---------+----------+...(*) FROM gravity_t1 group by (user_id%4); +---------+----------+ | hash_id | count(*) | +---------+--...=0; delete from t1_shard2 where user_id %4!=1; delete from t1_shard3 where user_id %4!... FROM gravity_t1 group by (user_id%4); select count(*) FROM t1_shard1 where user_id%4=0; select count
OK, 1 row affected (0.08 sec) MySQL> update flink_tab set clicks=2 where user='Mary'; Query OK, 1 row...引起上面变化的DML如下: MySQL> insert into flink_tab(user, clicks) values ('Llz', 1); Query OK, 1 row affected...(0.08 sec) MySQL> update flink_tab set clicks=2 where user='Bob'; Query OK, 1 row affected (0.01 sec...AS SELECT region, count(id) AS order_cnt FROM order_tab GROUP BY region; -- 按订单数量分组统计具有相同订单数量的地区数量...根据这两种信息构造对应的数据操作指令; 小结 本篇以MySQL为例介绍了传统数据库的静态查询和利用MySQL的Trigger+DML操作来模拟持续查询,并介绍了Apache Flink上面利用增量模式完成持续查询
* GreatSQL社区原创内容未经授权不得随意使用,转载请联系小编并注明来源。...类似工具有binlog2sql、MyFlash、my2fback等,本工具基于my2fback、binlog_rollback工具二次开发而来。 2....in set (0.00 sec) mysql> show variables like 'innodb_log_group_home_dir'; +-------------------------...in set (0.00 sec) --查看测试表行数 mysql> select count(*) from sbtest.sbtest1; +----------+ | count(*) | +-...count(*) from sbtest.sbtest1; +----------+ | count(*) | +----------+ | 100000 | +----------+ 1 row
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