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解决MySQL Connector Net 8卸载不掉。本来安装的mysql-installer-community-8.0.23.0.msi，由于各种原因，需要调整为mysql-installer-community-5.7.34.0.msi，然后卸载mysql。但是MySQL Connector Net 8.0.23总是卸载不掉。解决：将同事的Connector NET 8.0 复制到电脑C:\Program Files (x86)\MySQL中，之后再卸载就可以卸载成功了。C.

多数据源多租户-动态切换数据源

SELECT T2.func_id, T2.func_name ,T1.parent_id,lvlFROM ( SELECT @r AS _id, (SELECT @r := parent_id FROM bp_func WHERE func_id = _id) AS parent_id, @l := @l + 1 AS lvl FROM (SELECT @r := 147, @l := 0) vars, .

SELECT table_name, column_name FROM information_schema.COLUMNS WHERE table_schema = 'database1' AND table_name NOT IN ( SELECT table_name FROM information_schema.COLUMNS WHERE table_schema = 'database1' AND column_name = 'sss_id' GROUP BY table_na.

偶现，从数据源中取不到jdbc连接org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:### Error querying database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Conn

-- dev手机号与userid的对应关系与test手机号与userid的对应关系不一致，希望查询出不一致的数据。-- dev库执行show variables like 'group_concat_max_len';SET SESSION group_concat_max_len = 102400000;SELECT GROUP_CONCAT( "'", user_id, "_", mobile, "'" ) AS usercodeFROM dev.user;-- 查询结...

UPDATE 表名 SET 字段名 = REPLACE ( 字段名, '被替换字符串', '用来替换的字符串' );UPDATE table_1SET url= REPLACE ( url, 'http://baidu.com', 'https://baidu.com' );

查询 指定数据库 表数据量记录一下SELECT table_schema AS '数据库', table_name AS '表名', table_rows AS '记录数', TRUNCATE ( data_length / 1024 / 1024, 2 ) AS '数据容量(MB)', TRUNCATE ( index_length / 1024 / 1024, 2 ) AS '索引容量(MB)'FROM information_schema.tab...

A表 员工部门中间表B表 员工考勤表背景：员工考勤表 部门id字段缺失，批量修复B表数据，填充部门idsqlUPDATE BbINNER JOIN A aON a.staff_id = CONVERT ( b.staff_id USING utf8 ) COLLATE utf8_unicode_ciSET a.dept_id = b.dept_idWHERE...