Chapter 7. Constructing Simple Database Queries

In most databases, the vast majority of SQL statements issued are designed to retrieve information from a database. You can use the SQL SELECT statement to retrieve information from database tables. The beauty of this statement is that it's quite simple to use in its basic form, but it also contains quite a bit of flexible power, allowing you to precisely specify the exact information you'd like to retrieve.

In this chapter, I dissect the SELECT statement, clause-by-clause, and show you how to put together simple database queries. I recommend that you master this material before you check out the more powerful uses of the SELECT statement that I present in Chapter 8.

Retrieving Data with SELECT Statements

The SQL command used to retrieve data from a database is the SELECT statement. As do other SQL statements, the SELECT statement reads almost like an English statement. If you can fill in the blanks in the following sentence, you can compose a SELECT statement:

Select ____columns____ from ___table___ where ____
          conditions____.

That's really all there is to it. You simply need to identify three things to compose a proper SELECT query:

  • The columns you want to retrieve

  • The table you want to retrieve them from

  • The conditions (if any) that the data must satisfy

You then take this information and plug it into the proper SQL syntax. For example, suppose you wanted to retrieve a list of students from a school database to determine which students might ...

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