Programming the Perl DBI

Modifying Data Within Tables

Read-only databases (that is, databases that only allow you to SELECT data from them) are very useful. Data warehouses are typically massive read-only databases populated with archived data mangled into a form suitable for reporting. However, in the cut-and-thrust world of transaction-processing databases, the ability to modify data within the database quickly and efficiently is of paramount importance.

There are several core operations that comprise the broader definition of data modification, namely:

• Inserting new data into the database

• Deleting data from the database

• Updating, or modifying, existing data within the database

Each of these operations falls into the grouping of Data Manipulation Language commands, or DMLs, alongside SELECT.

We shall discuss each of these tasks in turn and apply the theory to our example database.