Saturday, 28 February 2015

Review 5.2: Perform a Query in Search Engine Database

Perform a Query in Search Engine Database

After the database for the search engine was constructed, sql queries needed to be used to get the result what users intend to get.

In order to make it easy to understand, A example is shown as the following. Suppose a user searches "c programming language". Then we can guess this user want to browse some webpages introducing how to program using c. So all the webpages should have all the three words. Hence, we can use a SQL statement like 

SELECT w0.urlid, w0.location , w1.location , w2.location
FROM wordlocation as w0, wordlocation as w1, wordlocation as w2
WHERE w0.urlid = w1.urlid
AND w1.urlid = w2.urlid
AND w0.wordid = ("C"'s rowid in table wordlist)
AND w1.wordid = ("programming"'s rowid in table wordlist)
AND w2.wordid = ("language"'s rowid in table wordlist) 

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