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Searching a MySQL Database

Constructing Search Queries. Searching a MySQL Database. IR’s “Bag of Words” Model. Typical IR data model: Each document is just a bag (multi-set) of words (“terms ”) Detail 1: “Stop Words” Certain words are considered irrelevant and not placed in the bag e.g., “the”

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Searching a MySQL Database

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  1. Constructing Search Queries Searching a MySQL Database

  2. IR’s “Bag of Words” Model • Typical IR data model: • Each document is just a bag (multi-set) of words (“terms”) • Detail 1: “Stop Words” • Certain words are considered irrelevant and not placed in the bag • e.g., “the” • e.g., HTML tags like <H1> • Detail 2: “Stemming” and other content analysis • Using English-specific rules, convert words to their basic form • e.g., “surfing”, “surfed” --> “surf” • Database Management Systems, R. Ramakrishnan

  3. Boolean Text Search • Find all documents that match a Boolean containment expression: • “Windows” AND (“Glass” OR “Door”)  AND NOT “Microsoft” • Note: Query terms are also filtered via stemming and stop words. • When web search engines say “10,000 documents found”, that’s the Boolean search result size (subject to a common “max # returned’ cutoff). • Database Management Systems, R. Ramakrishnan

  4. SQL Logical Operators • There are three Logical Operators: AND, OR, and NOT. • These operators compare two conditions at a time to determine whether a row can be selected for the output. • When retrieving data using a SELECT statement, you can use logical operators in the WHERE clause, which allows you to combine more than one condition. http://beginner-sql-tutorial.com/sql-logical-operators.htm

  5. "OR" Logical Operator: • If you want to select rows that satisfy at least one of the given conditions, you can use the logical operator, OR. • For example: if you want to find the names of students who are studying either Math or Science, the query would be like, • The following table describes how logical "OR" operator selects a row. http://beginner-sql-tutorial.com/sql-logical-operators.htm

  6. "AND" Logical Operator: • If you want to select rows that must satisfy all the given conditions, you can use the logical operator, AND. • For Example: To find the names of the students between the age 10 to 15 years, the query would be like: • The following table describes how logical "AND" operator selects a row. http://beginner-sql-tutorial.com/sql-logical-operators.htm

  7. "NOT" Logical Operator: • If you want to find rows that do not satisfy a condition, you can use the logical operator, NOT. NOT results in the reverse of a condition. That is, if a condition is satisfied, then the row is not returned. • For example: If you want to find out the names of the students who do not play football, the query would be like: • The following table describes how logical "NOT" operator selects a row. http://beginner-sql-tutorial.com/sql-logical-operators.htm

  8. Nested Logical Operators: • You can use multiple logical operators in an SQL statement. When you combine the logical operators in a SELECT statement, the order in which the statement is processed is • 1) NOT 2) AND 3) OR • For example: If you want to select the names of the students whose age is between 10 and 15 years, or those who do not play football, the SELECT statement would be • The filter works as follows: • Condition 1: All the authors not Smith are selected.Condition 2: All the articles dated between 1/23/10 and 2/16/10 are selected.Condition 3: Finally the result is, the rows which satisfy at least one of the above conditions is returned. • NOTE: The order in which you phrase the condition is important, if the order changes you are likely to get a different result. http://beginner-sql-tutorial.com/sql-logical-operators.htm

  9. Boolean Operators • OR – increases recall (gets more) • AND – Increases precision (gets less)

  10. Building Search into your Application • First decide which fields in your table(s) will be searchable. • Second, Before you code anything in PHP, use PHPMyAdmin or some other utility to test the SQL statement you will use to search your data. • Third, add the SQL statement to your PHP code. • Forth, the PHP script should use ‘pagination’ – if you have 100 results, it should break it up into pages i.e. 5 pages of 20 results each or 10 pages of 10 results each. • Fifth, each result should link back to the actual article, recipe, image etc. • Sixth, any other enhancements you want to add.

  11. Resources • SQL Logical Operators • http://beginner-sql-tutorial.com/sql-logical-operators.htm • PHP search engine - • http://www.roscripts.com/PHP_search_engine-119.html • Autosuggest/autocomplete from database - • http://www.roscripts.com/Ajax_autosuggest_autocomplete_from_database-154.html

  12. Resources • PHP / MySQL select data and split on pages • http://www.phpjabbers.com/phpexample.php?eid=25 • PHP Basic Pagination • http://www.phpfreaks.com/tutorial/basic-pagination • Perfect PHP Pagination • http://articles.sitepoint.com/article/perfect-php-pagination • Tag Schema • http://forge.mysql.com/wiki/TagSchema

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