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.
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