A Look at SQL Queries

by Andrew H
For this weeks blog post I read an academic journal by Mohammad Dadashzadeh called, “A Simpler Approach to Set Comparison Queries in SQL.” The article talks about set comparison queries which are queries that have results that can only be determined by comparing two sets of data. An example of a comparison query would be Which suppliers will be able to supply all the parts that they are currently shipping or which suppliers are shipping exactly the same parts as supplier SI? In contrast to these two queries a query such as “which suppliers are shipping at least one red part” can be obtained by matching or joining data from one table. The article explains how queries involving set comparison are very difficult to formulate in relational query languages because they must use the error prone EXISTS function. Their solution is to avoid the EXIST function and use the built in SET function as well as the COUNT function.

I thought this article was interesting because it has to do with comparison queries and we have not talked much about them. The article caught my eye because it said a simpler approach and I like when things are broken down and explained well. I found that the article was written pretty well even though it did not break it down as much as I had hoped it would. It was very helpful in explaining what causes errors and how to avoid them. I thought the article was very helpful and this is something that can possibly help other students.

Dadashzadeh, M. (2003). A Simpler Approach to Set Comparison Queries in SQL. Journal of Information Systems Education, 14,  345-348.

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