1、模糊查询字段含有的指定的内容 select *from tablename where user like ‘%指定的字符串%‘
精确的查找 select *from tablename where user substring(user,‘指定位置‘，‘长度’)==‘指定值’
2、查找字段值重复的次数
SELECT writer,count(*) as totals from tablename where writer=‘值‘ having count(1)>0
原文：https://www.cnblogs.com/zhangzhonglin2018/p/9476253.html