If you’ve used Oracle, SQL Server, MySQL, DB2, or other database engines, then SQL should be old hat to you. You can skip this section and go to Hello, Database. For the rest of you, here’s a quick refresher.
To use a SQL database, you submit SQL statements and get back results. There are three main types of SQL statements: DDL, Modification, and Query.
A database file can have any number of tables. A table consists of rows, and each row has a certain number of columns. Each column of the table has a name and a data type (text string, number, and so forth). You define these tables and column names by first running Data Definition Language (DDL) statements. Here’s a statement that creates a table with three columns: