wang20y8的博客

pgsql 多行转一行

ORDER BY FIELD(businessType,"POU","CO","STO","BUY_BACK", "SELL") ASC

administrator 运行cmd ，然后进入mysql安装路径D:\mysql-8.0.17-winx64\bin查看一下加密的方式：show variables like 'default_authentication_plugin';查看本地mysql用户的信息：select host,user,plugin from mysql.user;修改root账户的加密方式为（mysql_native_password）：ALTER USER 'root'@'lo...

select * FROM gov_safety_helmet_alarm WHERE create_time >= CURRENT_TIMESTAMP - INTERVAL 10 MINUTE

改后的sql

今天遇到一个惊天大bug，查询数据库版本select version();mysql 5.6SELECT aa.worker_status,aa.worker_id,aa.create_time,aa.project_id FROM( SELECT twe.worker_id,twe.worker_status,twe.project_id,twe.create_time...

1.使用like，但是like在前面加%会让索引失效SELECT count(1) FROM t_project WHERE project_address LIKE('%烟台市%');2.使用LOCATE(substr,str)函数/LOCATE(substr,str,pos)SELECT count(1) FROM t_project WHERE LOCATE('烟台市',proj...

索引的目标是防止全表扫描(Full Scan)1.从存储结构划分：BTree索引(B-Tree或者B+Tree索引)，Hash索引,full-index全文索引，B-Tree索引2.从应用层来划分：普通索引，唯一索引，复合索引3.根据数据的物理顺序与键值的逻辑顺序：聚集索引，非聚集索引B+Tree索引-适合范围查找Hash索引-适合精准匹配...

完整错误信息：ERROR:1118 - Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. This includes storage overhead, check the manual. You have to change some columns to...

第一篇讲的是直接套用mysql函数定义来实现拼音分组和排序https://blog.youkuaiyun.com/wang20y8/article/details/80753605这一篇通过mysql function(函数) 进行实现，直接贴代码：DELIMITER $$      CREATE FUNCTION `fristPinyin`(        P_NAME VARCHAR(25...

查询系统当前时间，不带时分秒，如：2018-11-02==>SELECT CURDATE();日期相减函数，获取天数：datediff(CURDATE(), '2018-01-01')下面一个demo：SELECT CASE WHEN datediff(CURDATE(), a.year_for_car) < 180 THEN '6个月以下'WHEN 180<...

在insert标签中加入keyProperty="id" useGeneratedKeys="true"属性,对应的mapper.java文件service实现层获取对象的id

Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation '= 其实是表和表之间的字符编码不匹配造成的，要么修改表字段的字符编码，要么就加函数 SELECT a.id, a.step, a.title, a.content, c.path ste...

1055 - Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'queqiao.a.iid' which is not functionally dependent on columns in GROUP BY clause; this is incompatible ...