The Structured Query Language (SQL) forms the backbone of most modern database systems. These links provide the best resources on the Net for neophytes and expert database administrators alike!
Counting Values in a Database Table with the SQL COUNT Function
The COUNT() function in SQL allows you to count database records based upon a variety of criteria. You can use it to count all records in a table, count unique values in a column or count the number of times records occur that meet certain criteria. This tutorial takes a brief look at each of these scenarios.
Combining Query Results with the UNION Command
SQL’s UNION command allows you to combine the results of two or more database queries that are not necessarily linked through a database relationship. For example, imagine that you have a school database and wish to use it to create a master contact list for all students, faculty and staff. Looking at your database, you discover that the records corresponding to each of these constituencies appears in separate database tables.
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