选择某表的某列从某表
select tablesname.column from tables;
选择某表的某列从某库的某表
select tablesname.column from database.tables
选择某表从某列按照某列的顺序
select column from database order by column；
选择多列从某表按照某两列排序
select column1,column2,c3 from database order by column1,column2；
选择多列从某表按照某列降序排序
select column1,column2,c3 from database order by column1 desc；
查询某行从某表以某行排序取最值
select column from tables order by column1 desc limit 1;
