What is SQL?
SQL stands for structured query language and has been around for decades. The primary purpose of SQL is to retrieve and store data from and to a relational database. The database server, itself, must be SQL compliant and while there are many providers of SQL servers the only ones Infocus works with are Microsoft SQL 2005 and Microsoft SQL 2008.
The select statement is a single organized statement that has distinct sections (called clauses) in an exact order. A select statement returns a single set of columns and rows known as a dataset. A dataset can be thought of as a two-dimensional spreadsheet. The following sections are the most commonly used. They are listed in the necessary order.
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In the previous lesson we learned how to query data from a single table. In this lesson we will learn how to retrieve data from multiple tables. We do this by using what is known as JOINS.
In this lesson our examples will all revolve around querying for project metrics. In order to do that we need to learn the UNION clause. The union clause allows us to take two or more SELECT statements and return them as one dataset. The rule for UNIONS is that each of the select statements must bring back the same number of columns and each column in the order listed must have the same data type . The first example will bring back cost for all projects. In order to bring back cost we need data from the timesheets and three journals; employee reimbursable, purchases and disbursements. This example will bring back the transaction ID, the cost amount, the journal of entry, the project path and the project long name. The project being returned is the top level project node in the WBS.