返回指定行数之间的查询结果
2024-07-21 02:38:43
供稿：网友
如何返回指定行数之间的查询结果，以实现web记录分页，在Oracle中有许多的方法，这里仅仅列出了4种，希望能对大家有所帮助，大家可以根据不同需要选择下面的script
1）select ... where rownum < 50 minus select ... where rownum < 30
这个方法因为用到了minus操作符，所以速度会受影响。
2）
SELECT results.* FROM
( SELECT t2.*, rownum rownumber FROM
( SELECT t.* FROM mv_table t WHERE ORDER BY col1) t2) results
WHERE results.rownumber BETWEEN 30 and 50 ORDER BY col1
3）
定义cursor x, 2.fetch x a,b,c; loop ...... end loop;
其中用两个循环变量和一个FLAG变量，分别表示，当前的记录数，属于第几页的， 及第一页面。
ps;
j:=to_number(kafyf);
i:=1;
open cx;
loop fetch cx into col1,col2,col3,col4,col5,col6;
if cx%NOTFOUND then exit; end if;
if i>=j then
htp.tableRowOpen;
htp.tableData(col1);
htp.tableData(col2);
htp.tableData(col4);
htp.tableData(col5);
htp.tableData(col6);
htp.tableData(col3);
htp.tableRowClose;
i:=i+1;
if i=j+10 then l:=1; exit; end if;
else i:=i+1;
end if;
end loop;
close x;
该方法用到了Oracle web2kit中的OWA_UTIL package。
4）How can one page forward and backwards through a table?
Externalize ROWNUM by implementing queries like this:
SELECT ...
FROM (SELECT ROWNUM rnum, ... FROM ...)
WHERE rnum BETWEEN :low AND :high AND rownum <(:high :low + 1);
where :low and :high are dynamically generated values depending on which result page the user
is viewing. Typically, they are used to show "Next 15 matches", "PRevious 15 matches" links at the
bottom of each page.
