可以用來進行全前N條記錄，或者分頁操作。Oracle SQL如下：select * from sometable where rownum <= 100; select * from sometable where rownum > 100 and rownum <= 200; SELECT * FROM ( SELECT A.*,ROWNUM AS RN FROM (SELECT * FROM sometable order by col) A WHERE ROWNUM <= 200) T WHERE T.RN > 100Informix 有更簡單、高效的分頁功能： select first 100 * from sometable; select skip 100 first 100 * from sometable; select skip 100 first 100 * from sometable order by col;記錄編號：在ORACLE中，可以直接通過rownum 得到每條記錄的一個編號，select rownum, * from sometable ; Informix中需要通過創建一個存儲過程來實現類似功能。 CREATE FUNCTION rownum () returning int as rownum; define global counter int default 0; let counter = counter + 1; return counter; end function; CREATE PROCEDURE init_rownum (); define global counter int default 0; let counter = 0; end procedure; 可以按如下方式使用函數反問記錄編號。

用序列
Use the CREATE SEQUENCE statement to create a sequence database object from
which multiple users can generate unique integers.