Data Definition Language (DDL): Part 1

In this video we start to look at the DDL (Data Definition Language) part of SQL (Structured Query Language). The DDL is what is used to CREATE a database -- to specify what data will be collected, what values are allowed, and so on. We start with the narrowest part -- defining attributes. To start an attribute has a name or identifier. Next, it has a type to limit the sort of values that are expected to be stored (text or numbers or simple true/false values). One can introduce further restriction by defining a DOMAIN and using a CHECK to ensure the inserted or updated value falls within the domain. With each attribute one can specify whether a value of NULL is allowed. One can also implement a DEFAULT value to use if none is supplied in the INSERT.