1.连接数据库mysql -u root -p远程数据库mysql -u root -p -h 192.168.1.100 -P 33072.导出mysqldump -u 用户名 -p 数据库名>/mnt/usb/testdb.sqlmysqldump -u root -p testdb>/mnt/usb/testdb.sql远程数据库mysqldump -h 主机 -P 端口 -u 用户名 -p 数据库名>/mnt/usb/testdb.sqlmysqldump -h 192.168.1.100 -P 3307 -u root -p testdb>/mnt/usb/testdb.sql3.导入mysql -u 用户名 -p 数据库名</mnt/usb/testdb.sqlmysql -u root -p testdb</mnt/usb/testdb.sql4.定制导出脚本USER_NAME=$1 if [ ! -n "$USER_NAME" ]; then echo "User name can't be empty!" exit 0 fi PWD=$2 if [ ! -n "$PWD" ]; then echo "Password name can't be empty!" exit 0 fi echo "Password is $PWD" DB_NAME=$3 if [ ! -n "$DB_NAME" ]; then echo "Database name can't be empty!" exit 0 fi PORT=$4 if [ ! -n "$PORT" ]; then PORT=3306 fi BACK_PATH=$5 if [ ! -n "$BACK_PATH" ]; then BACK_PATH='./db-back' fi HOST=$6 if [ ! -n "$HOST" ]; then HOST='127.0.0.1' fi BACK_FILE_NAME=_"$PORT"_$(date '+%Y%m%d%H%M%S') if [ -a $BACK_PATH ]; then echo "Back path is '$BACK_PATH'." else mkdir $BACK_PATH fi cd $BACK_PATH mysqldump -h $HOST -P $PORT -u$USER_NAME -p$2 $DB_NAME>$DB_NAME$BACK_FILE_NAME.sqldemosh backup.sh root 111111 dbname 3306 /mnt/usb/db-backup
在整个MySQL数据库中查找select * from INFORMATION_SCHEMA.columns where COLUMN_NAME Like '%placement%';在特定数据库中查找SELECT DISTINCT TABLE_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE COLUMN_NAME IN ('ColumnA','ColumnB') AND TABLE_SCHEMA='DatabaseName'; SELECT DISTINCT TABLE_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE COLUMN_NAME LIKE '%ColumnA%' AND TABLE_SCHEMA='DatabaseName';在特定数据库中查找包含A和B字段的表SELECT DISTINCT * FROM INFORMATION_SCHEMA.COLUMNS WHERE COLUMN_NAME IN ('A') and TABLE_NAME in (SELECT DISTINCT TABLE_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE COLUMN_NAME IN ('B') AND TABLE_SCHEMA='DatabaseName')
1.SET UPDATE t_user status =#{status}, run_status =#{runStatus}, WHERE id=#{id} 2.DELETE/删除指定条数 DELETE from t_user WHERE id = #{id} LIMIT #{num} 3.choose-when结构/IFNULL/MAX/ INSERT INTO t_robot_chat_expand (chat_word_id,sort, content ) VALUES( #{chatWordId}, (SELECT IFNULL(MAX( RCE.sort ) + 1,0) FROM t_robot_chat_expand RCE WHERE RCE.chat_word_id = #{chatWordId} ), IF((SELECT MAX( RCE.sort ) FROM t_robot_chat_expand RCE WHERE RCE.chat_word_id = 1 ) < #{sort}, (SELECT MAX( RCE.sort ) + 1 FROM t_robot_chat_expand RCE WHERE RCE.chat_word_id = #{chatWordId} ), #{sort}), #{content})
mysql更新移除逗号分割字符串中部分字符
UPDATE t_robot_team SET chat_words = TRIM(BOTH ',' FROM REPLACE( CONCAT( ',', chat_words, ',' ), CONCAT( ',', 21, ',' ), ',' )) WHERE locate(CONCAT(',',21,','),CONCAT(',',chat_words,','));
1.从某张表随机取一条记录简单，低效SELECT * FROM table_name ORDER BY RAND() LIMIT 1；速度快，效率高SELECT t1.id, t1.word, t1.STATUS FROM hy_idiom AS t1 JOIN ( SELECT ROUND( RAND() * (( SELECT MAX( id ) FROM hy_idiom WHERE STATUS = 1 )-( SELECT MIN( id ) FROM hy_idiom WHERE STATUS = 1 ))+ ( SELECT MIN( id ) FROM hy_idiom WHERE STATUS = 1 ) ) AS id ) AS t2 WHERE t1.id >= t2.id AND t1.STATUS = 1 ORDER BY t1.id LIMIT 5;SELECT T1.* FROM ( SELECT (@RN := @RN + 1) AS sort, U.* FROM t_user U, (SELECT @RN := -1) AS T11 ) T1 JOIN( SELECT FLOOR( rand()*( SELECT COUNT(1) FROM t_user ) ) AS sort ) T2 ON T1.sort = T2.sort2.从表总记录数取随机序号SELECT FLOOR( rand()*( SELECT COUNT(*) FROM t_user ) );3.显示某张表序号/行号SELECT (@RN := @RN + 1) AS sort, id FROM t_user, (SELECT @RN := -1) AS T0
使用explain+SQL语句来模拟优化器执行SQL查询语句
mysql执行计划​ 在企业的应用场景中，为了知道优化SQL语句的执行，需要查看SQL语句的具体执行过程，以加快SQL语句的执行效率。​ 可以使用explain+SQL语句来模拟优化器执行SQL查询语句，从而知道mysql是如何处理sql语句的。​ 官网地址： https://dev.mysql.com/doc/refman/5.5/en/explain-output.html1、执行计划中包含的信息ColumnMeaningidThe SELECT identifierselect_typeThe SELECT typetableThe table for the output rowpartitionsThe matching partitionstypeThe join typepossible_keysThe possible indexes to choosekeyThe index actually chosenkey_lenThe length of the chosen keyrefThe columns compared to the indexrowsEstimate of rows to be examinedfilteredPercentage of rows filtered by table conditionextraAdditional informationidselect查询的序列号，包含一组数字，表示查询中执行select子句或者操作表的顺序id号分为三种情况：​ 1、如果id相同，那么执行顺序从上到下explain select * from emp e join dept d on e.deptno = d.deptno join salgrade sg on e.sal between sg.losal and sg.hisal;​ 2、如果id不同，如果是子查询，id的序号会递增，id值越大优先级越高，越先被执行explain select * from emp e where e.deptno in (select d.deptno from dept d where d.dname = 'SALES');​ 3、id相同和不同的，同时存在：相同的可以认为是一组，从上往下顺序执行，在所有组中，id值越大，优先级越高，越先执行explain select * from emp e join dept d on e.deptno = d.deptno join salgrade sg on e.sal between sg.losal and sg.hisal where e.deptno in (select d.deptno from dept d where d.dname = 'SALES');select_type主要用来分辨查询的类型，是普通查询还是联合查询还是子查询select_type ValueMeaningSIMPLESimple SELECT (not using UNION or subqueries)PRIMARYOutermost SELECTUNIONSecond or later SELECT statement in a UNIONDEPENDENT UNIONSecond or later SELECT statement in a UNION, dependent on outer queryUNION RESULTResult of a UNION.SUBQUERYFirst SELECT in subqueryDEPENDENT SUBQUERYFirst SELECT in subquery, dependent on outer queryDERIVEDDerived tableUNCACHEABLE SUBQUERYA subquery for which the result cannot be cached and must be re-evaluated for each row of the outer queryUNCACHEABLE UNIONThe second or later select in a UNION that belongs to an uncacheable subquery (see UNCACHEABLE SUBQUERY)--sample:简单的查询，不包含子查询和union explain select * from emp; --primary:查询中若包含任何复杂的子查询，最外层查询则被标记为Primary explain select staname,ename supname from (select ename staname,mgr from emp) t join emp on t.mgr=emp.empno ; --union:若第二个select出现在union之后，则被标记为union explain select * from emp where deptno = 10 union select * from emp where sal >2000; --dependent union:跟union类似，此处的depentent表示union或union all联合而成的结果会受外部表影响 explain select * from emp e where e.empno in ( select empno from emp where deptno = 10 union select empno from emp where sal >2000) --union result:从union表获取结果的select explain select * from emp where deptno = 10 union select * from emp where sal >2000; --subquery:在select或者where列表中包含子查询 explain select * from emp where sal > (select avg(sal) from emp) ; --dependent subquery:subquery的子查询要受到外部表查询的影响 explain select * from emp e where e.deptno in (select distinct deptno from dept); --DERIVED: from子句中出现的子查询，也叫做派生类， explain select staname,ename supname from (select ename staname,mgr from emp) t join emp on t.mgr=emp.empno ; --UNCACHEABLE SUBQUERY：表示使用子查询的结果不能被缓存 explain select * from emp where empno = (select empno from emp where deptno=@@sort_buffer_size); --uncacheable union:表示union的查询结果不能被缓存：sql语句未验证table对应行正在访问哪一个表，表名或者别名，可能是临时表或者union合并结果集 1、如果是具体的表名，则表明从实际的物理表中获取数据，当然也可以是表的别名 ​ 2、表名是derivedN的形式，表示使用了id为N的查询产生的衍生表​ 3、当有union result的时候，表名是union n1,n2等的形式，n1,n2表示参与union的idtypetype显示的是访问类型，访问类型表示我是以何种方式去访问我们的数据，最容易想的是全表扫描，直接暴力的遍历一张表去寻找需要的数据，效率非常低下，访问的类型有很多，效率从最好到最坏依次是：system > const > eq_ref > ref > fulltext > ref_or_null > index_merge > unique_subquery > index_subquery > range > index > ALL 一般情况下，得保证查询至少达到range级别，最好能达到ref--all:全表扫描，一般情况下出现这样的sql语句而且数据量比较大的话那么就需要进行优化。 explain select * from emp; --index：全索引扫描这个比all的效率要好，主要有两种情况，一种是当前的查询时覆盖索引，即我们需要的数据在索引中就可以索取，或者是使用了索引进行排序，这样就避免数据的重排序 explain select empno from emp; --range：表示利用索引查询的时候限制了范围，在指定范围内进行查询，这样避免了index的全索引扫描，适用的操作符： =, <>, >, >=, <, <=, IS NULL, BETWEEN, LIKE, or IN() explain select * from emp where empno between 7000 and 7500; --index_subquery：利用索引来关联子查询，不再扫描全表 explain select * from emp where emp.job in (select job from t_job); --unique_subquery:该连接类型类似与index_subquery,使用的是唯一索引 explain select * from emp e where e.deptno in (select distinct deptno from dept); --index_merge：在查询过程中需要多个索引组合使用，没有模拟出来 explain select * from rental where rental_date like '2005-05-26 07:12:2%' and inventory_id=3926 and customer_id=321\G --ref_or_null：对于某个字段即需要关联条件，也需要null值的情况下，查询优化器会选择这种访问方式 explain select * from emp e where e.mgr is null or e.mgr=7369; --ref：使用了非唯一性索引进行数据的查找 create index idx_3 on emp(deptno); explain select * from emp e,dept d where e.deptno =d.deptno; --eq_ref ：使用唯一性索引进行数据查找 explain select * from emp,emp2 where emp.empno = emp2.empno; --const：这个表至多有一个匹配行， explain select * from emp where empno = 7369; --system：表只有一行记录（等于系统表），这是const类型的特例，平时不会出现possible_keys ​ 显示可能应用在这张表中的索引，一个或多个，查询涉及到的字段上若存在索引，则该索引将被列出，但不一定被查询实际使用explain select * from emp,dept where emp.deptno = dept.deptno and emp.deptno = 10;key​ 实际使用的索引，如果为null，则没有使用索引，查询中若使用了覆盖索引，则该索引和查询的select字段重叠。explain select * from emp,dept where emp.deptno = dept.deptno and emp.deptno = 10;key_len表示索引中使用的字节数，可以通过key_len计算查询中使用的索引长度，在不损失精度的情况下长度越短越好。explain select * from emp,dept where emp.deptno = dept.deptno and emp.deptno = 10;ref显示索引的哪一列被使用了，如果可能的话，是一个常数explain select * from emp,dept where emp.deptno = dept.deptno and emp.deptno = 10;rows根据表的统计信息及索引使用情况，大致估算出找出所需记录需要读取的行数，此参数很重要，直接反应的sql找了多少数据，在完成目的的情况下越少越好explain select * from emp;extra包含额外的信息。--using filesort:说明mysql无法利用索引进行排序，只能利用排序算法进行排序，会消耗额外的位置 explain select * from emp order by sal; --using temporary:建立临时表来保存中间结果，查询完成之后把临时表删除 explain select ename,count(*) from emp where deptno = 10 group by ename; --using index:这个表示当前的查询时覆盖索引的，直接从索引中读取数据，而不用访问数据表。如果同时出现using where 表名索引被用来执行索引键值的查找，如果没有，表面索引被用来读取数据，而不是真的查找 explain select deptno,count(*) from emp group by deptno limit 10; --using where:使用where进行条件过滤 explain select * from t_user where id = 1; --using join buffer:使用连接缓存，情况没有模拟出来 --impossible where：where语句的结果总是false explain select * from emp where empno = 7469;
忽略大小写8.0.26docker run -d --name=db3307 -p 3307:3306 -e MYSQL_ROOT_PASSWORD=111111 mysql:8.0.26 --lower_case_table_names=15.7.35docker run -d --name=db3307 -p 3307:3306 -e MYSQL_ROOT_PASSWORD=111111 mysql:5.7.35 --lower_case_table_names=1需要挂载目录的话：docker run -p 3307:3306 --name=db3307 \ --privileged=true \ --restart unless-stopped \ -v /opt/docker/mysql/conf:/etc/mysql \ -v /opt/docker/mysql/logs:/logs \ -v /opt/docker/mysql/data:/var/lib/mysql \ -v /etc/localtime:/etc/localtime \ -e MYSQL_ROOT_PASSWORD=111111 \ -d mysql:8.0.26 \ --lower_case_table_names=1创建数据库命令CREATE DATABASE `testdb` CHARACTER SET 'utf8mb4' COLLATE 'utf8mb4_0900_ai_ci';解决问题Caused by: java.sql.SQLSyntaxErrorException: Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'cpms_v2.cpms_project.id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_bySHOW VARIABLES LIKE '%case%'; SET GLOBAL sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
1.清理指定id的小说所有内容DROP PROCEDURE IF EXISTS clear_invalid_novel; CREATE PROCEDURE clear_invalid_novel() BEGIN DECLARE bookid varchar(255) DEFAULT '1431094810327994368'; DELETE FROM book_content WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_content0 WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_content1 WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_content2 WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_content3 WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_content4 WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_content5 WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_content6 WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_content7 WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_content8 WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_content9 WHERE index_id in (SELECT id FROM book_index WHERE book_id=bookid); DELETE FROM book_index WHERE book_id=bookid; DELETE FROM book WHERE id=bookid; END; call clear_invalid_novel();2.删除无效的小说文本delete from book_content where index_id not in(SELECT id from book_index); delete from book_content0 where index_id not in(SELECT id from book_index); delete from book_content1 where index_id not in(SELECT id from book_index); delete from book_content2 where index_id not in(SELECT id from book_index); delete from book_content3 where index_id not in(SELECT id from book_index); delete from book_content4 where index_id not in(SELECT id from book_index); delete from book_content5 where index_id not in(SELECT id from book_index); delete from book_content6 where index_id not in(SELECT id from book_index); delete from book_content7 where index_id not in(SELECT id from book_index); delete from book_content8 where index_id not in(SELECT id from book_index); delete from book_content9 where index_id not in(SELECT id from book_index);3.整合表内容create table book_content_test as SELECT id, index_id,content from ( SELECT * FROM book_content0 B0 WHERE B0.index_id in (SELECT id FROM book_index WHERE book_id='1431142380391714816') union all SELECT * FROM book_content1 B1 WHERE B1.index_id in (SELECT id FROM book_index WHERE book_id='1431142380391714816') union all SELECT * FROM book_content2 B2 WHERE B2.index_id in (SELECT id FROM book_index WHERE book_id='1431142380391714816') union all SELECT * FROM book_content3 B3 WHERE B3.index_id in (SELECT id FROM book_index WHERE book_id='1431142380391714816') union all SELECT * FROM book_content4 B4 WHERE B4.index_id in (SELECT id FROM book_index WHERE book_id='1431142380391714816') union all SELECT * FROM book_content5 B5 WHERE B5.index_id in (SELECT id FROM book_index WHERE book_id='1431142380391714816') union all SELECT * FROM book_content6 B6 WHERE B6.index_id in (SELECT id FROM book_index WHERE book_id='1431142380391714816') union all SELECT * FROM book_content7 B7 WHERE B7.index_id in (SELECT id FROM book_index WHERE book_id='1431142380391714816') union all SELECT * FROM book_content8 B8 WHERE B8.index_id in (SELECT id FROM book_index WHERE book_id='1431142380391714816') union all SELECT * FROM book_content9 B9 WHERE B9.index_id in (SELECT id FROM book_index WHERE book_id='1431142380391714816') ) as T1;