Why we use Lucene for Database search like Oracle / Sybase ?

[Vikas Khengare]

Hi Friends,
 
        I have very basic question that
 
    1] Why we use Lucene for Database search like Oracle / Sybase ?
    2] For that first we have to convert all records one bye one in
string then build lucene document and then index it ?
 
Thanks
 
From,
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