AD_APPLIED_PATCHES holds information about the "distinct" Oracle Applications patches that have been applied. If 2 patches happen to have the same name but are different in content (eg. "merged" patches), then they are considered distinct and this table will therefore hold 2 records.

Ad_applied_patches contains information about patches that you applied on the system,

ad_bugs has information about all bugs and patches that have been included in the patches you applied.

For example you apply merged patch merge123 it contains 5 patches
10001 10002 10003 …
ad_applied_patches – will have one record about merge123
ad_bugs – 5 records

Another example: you apply maintenance patch which includes 51 other
patches. In that case
ad_applied_patches – will have one record about maintenance patch
ad_bugs – 51 + 1

I use ad_bugs table in order to find out do I have one or another patch to apply.

本文转自ITPUB博客tolywang的博客，原文链接：AD_BUGS 和 AD_APPLID_PATCHES 的区别，如需转载请自行联系原博主。