Databases vs. Search Engines

Full-text search engines evolved much later than traditional database engines, as corporations and governments found themselves with more and more unstructured textual data in electronic format. These new text documents didn't fit well into the old table-style databases, so the need for unstructured full-text searching was apparent.
Since it was developed later, search engine technology borrowed heavily from the database world, and many search engines still employ some type of traditional table structures in their underlying architecture. Some text retrieval companies were even staffed with employees who came from traditional database company backgrounds. Many of the traditional RDBMS (Relational Database Management System) paradigms have also migrated into search engine technology, though often renamed or recast.
Technical Similarities
While relational database systems and full-text search engines are optimized to process fundamentally different types of data, there are a number of similarities between the two.
.Both can search through large amounts of data
.Query Processing, Return Matching Records
.Data Loading
.Data Indexing
Technical Differences
While there are similarities between full-text and relational technologies, there are a number of differences as well because of the fundamental differences between the types of data being indexed and the flexibility of the retrieval options. While the differences can present some challenges, they also present the opportunity to take advantage of the key features of full-text search to provide an innovative solution to the problem at hand.
.Differences in Technical Vocabulary 
.Data Structure 
.Query Syntax 
.Additional Full-Text Operators 
.Weighting 
.Different Usage Patterns
.Joins 
.Outer Joins 
.Simpler Table Structure in Full-Text Systems 
.Virtual Documents 
.Document Keys 
.Data Types and Document Formats









Comparison of Terms

Databases             Search Engines
"database"           Collection, Document Index or Catalog
Table                    Segment or Partition
Record                  Document, Page, URL, Record, Match or Hit
Field                     Field, Doc Attribute, Meta Data, Zone
Blob                      Zone
Index (verb)         Indexing, Spidering, Crawling
Index (noun)        Collection, Fulltext Index