Oracle的order by 使用小结

ORDER BY 是用来对select结果排序的，很简单，但是也总结一下吧。

1. 按列名排序，默认是升序的。
单列升序：select<column_name> from <table_name> order by <column_name>;
单列降序：select <column_name> from table_name order by <column_name> desc;
多列升序：select <column_one>, <column_two> from table_name order by <column_one>, <column_two>;
多列降序：select <column_one>, <column_two> from <table_name> order by <column_one> desc, <column_two> desc;
多列混合降序：select column_one, column_two from table_name order by column_one desc, column_two desc;


2. 按列的位序排序, 默认是升序
select * from <table_name> order by 1

3. NULL排序
空值在前：select <column_name> from <table_name> order by <column_name> NULLS FIRST;
空值在后：select <column_name> from <table_name> order by <column_name> NULLS LAST;