Oracle特殊语句

1.字母数字检查

select content ,nvl2(translate(substr(content,1,3),'\1234567890','\'),'is characters','is number') from CHAT_200702;

判断前三位是汉字还是字母
select substr(content,1,3) from CHAT_200702 where lengthb(substr(content,1,3))=2 （把2改成1就是字母了，等于2则是汉字）

2.记录定位：查询第4条

SELECT * FROM
(
SELECT A.*, rownum r
FROM
(
SELECT *
FROM ejc
ORDER BY recordno DESC
) A
WHERE rownum <= 4
) B
WHERE r >3