MySQL常用sql语句
1、指定字段后插入新字段
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
ALTER TABLE enn_clue ADD remark_type VARCHAR (1) COMMENT '备注类型' after buz_type, ADD remark VARCHAR (255) COMMENT '备注' after remark_type
2、修改列类型
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
ALTER TABLE enn_contract MODIFY COLUMN short_code VARCHAR (255), MODIFY COLUMN full_code VARCHAR (255)
3.not in的注意问题
not in 在字段值有null的情况下会导致所有的数据查询不到。
4.删除重复的数据只保留一条
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
DELETE FROM enn_trade_back_payment WHERE transaction_code IN ( SELECT a.transaction_code FROM ( SELECT transaction_code FROM `enn_trade_back_payment` WHERE `data_source` LIKE '%网银导入%' GROUP BY transaction_code HAVING count(transaction_code) > 1 ) a ) AND id NOT IN ( SELECT b.id FROM ( SELECT min(id) AS id FROM `enn_trade_back_payment` WHERE `data_source` LIKE '%网银导入%' GROUP BY transaction_code HAVING count(transaction_code) > 1 ) b )
【推荐】编程新体验,更懂你的AI,立即体验豆包MarsCode编程助手
【推荐】凌霞软件回馈社区,博客园 & 1Panel & Halo 联合会员上线
【推荐】抖音旗下AI助手豆包,你的智能百科全书,全免费不限次数
【推荐】博客园社区专享云产品让利特惠,阿里云新客6.5折上折
【推荐】轻量又高性能的 SSH 工具 IShell:AI 加持,快人一步