一. 字符串拼接 concat('asdf',str); 说明: 拼接asdf 和 str 二. 字符串截取 从左开始截取字符串 left(str, length) 说明:) as abstract from tablename 从右开始截取字符串 right(str,length) 说明:) as abstract from tablename 按长度截取字符串 substring(str, pos) substring(str, pos, length) 说明:substring(被截取字段…