Database Reference
In-Depth Information
Chapter 5. Altering Tables
Despite the best planning,you will need occasionally to change the structure or other as-
pects of your tables. We cannot imagine everything that we might want to do with a table,
or how the data might look when it's entered. Altering a table, though, is not very difficult.
Because of these factors, you shouldn't worry too much about getting the table structure
exactly right when creating a table. You should see tables as more fluid. Perhaps the term
table structure
makes that difficult to accept: the words
table
and
structure
have such rigid
senses to them. To offset these images, perhaps a modified version of a cliché would be
useful to give you a truer sense of the reality of table structures: they're not made of stone
or wood, but of digital confines that are easily altered. I suspect that sentence won't be
quoted much, but it's a useful perspective.
In this chapter, we will explore the ways to alter tables: how to add and delete columns,
how to change their data types, how to add indexes, and how to change table and column
options. This chapter will also include some precautions about potential data problems you
can cause when altering a table containing data.
