oracle与sqlserver小结

select * from all_users; 
select * from dba_users;
select * from user_users;

select * from v$instance;

select * from v$tablespace;

select * from dba_data_files;

SQLServer  select getdate();
Oracle     select sysdate from dual;

SQLServer  select * from tab where Order_date > '1990-04-13';
Oracle     select * from tab where Order_date > date '1990-04-13';

select count(*) from orders where book_name != 'java基础'
select count(*) from orders where not book_name = 'java基础'

select book_id,book_name from orders order by 1 desc,2 desc