隐式转换bug

执行下段SQL，结果报错，ORA-01722无效数字

SELECT *
  FROM (SELECT ROWNUM R, H.*
          FROM (SELECT T.ESEQID, T.ATTACHNAME, T.INFOCODE
                  FROM NEWSADMIN.ANN_BASINFO T
                 WHERE T.ATTACHTYPE = 0
                   AND T.NOTICEDATE >= TO_DATE('2013-04-09', 'YYYY-MM-DD')
                   AND T.ESEQID > 4975226049
                   AND t.sourcename <> '发行人网站'
                 ORDER BY T.ESEQID ASC) H ) W
 WHERE W.R between 1 and  50

我就很郁闷，调整成w.r > 50就可以了，一直在查rownum的原因，最后发现是隐式转换问题

T.ATTACHTYPE 字段是字符类型，执行计划中进行了to_Number()操作，所以这个字段存储了不可to_number的值，导致报错。至于为什么w.r >50 不报错，是因为plsql取了缓存又或者没取到那个出错的值。正确的如下

SELECT *
  FROM (SELECT ROWNUM R, H.*
          FROM (SELECT T.ESEQID, T.ATTACHNAME, T.INFOCODE
                  FROM NEWSADMIN.ANN_BASINFO T
                 WHERE T.ATTACHTYPE = '0'
                   AND T.NOTICEDATE >= TO_DATE('2013-04-09', 'YYYY-MM-DD')
                   AND T.ESEQID > 4975226049
                   AND t.sourcename <> '发行人网站'
                 ORDER BY T.ESEQID ASC) H ) W
 WHERE W.R between 1 and  50

此外，如果不使用order by排序应该考虑将rownum between 1 and 50 写在里面变成如下这样，效率很高

SELECT *
  FROM (SELECT ROWNUM R, H.*
          FROM (SELECT T.ESEQID, T.ATTACHNAME, T.INFOCODE
                  FROM NEWSADMIN.ANN_BASINFO T
                 WHERE T.ATTACHTYPE = 0
                   AND T.NOTICEDATE >= TO_DATE('2013-04-09', 'YYYY-MM-DD')
                   AND T.ESEQID > 4975226049
                   AND t.sourcename <> '发行人网站'
                   and rownum between 1 and 50
                ) H ) W
 WHERE W.R > 1