Conclusion

It's time again to look back and see what you've done. Here's what you've accomplished since the first review:

1. Drew up a preliminary list of columns and created a list of tables in which to put them.

   You ignored mission objectives and made tables that represented one and only one subject.

2. Took a first stab at putting those columns into tables.

3. Evaluated the columns to see if any were calculated or multivalue fields.

   You dealt with these by creating or deleting new fields.

4. Reviewed the tables for candidate keys and selected a primary key for each table.

5. Reviewed the columns for multivalue fields.

   You did a preliminary fix by creating new tables that included the multivalue field and the primary key of the original table.

At this point, you've no doubt begun to wonder, "Isn't this an awful lot of work to create a database? Isn't there a much simpler method that would do the trick?"

Let me try a mundane but perhaps useful analogy. Remember when you went out trick-or-treating on Halloween? When you got home, you had a ton of candy in your bag. Your dad might have taken all that candy and dumped it quickly into one big jar.

That quickly solved the immediate problem of where to store the candy. But what happened when you wanted to find and eat the miniature Milky Way you remember getting? It was probably hidden in the middle or stuck away at the bottom. You usually wound up dumping out the whole jar to get at it.

On the other hand, if your mom was a database designer, she probably had you carefully sort and arrange the contents, allotting different goodies to different compartments in different containers. Initially, that took a lot longer than stuffing everything in a jar, but afterward you quickly and easily found the Milky Ways when you needed them. In the long run, the time spent organizing your plunder was well worth the effort.

In the next chapter, you'll see how keys are used to create relationships between tables, which enables you to combine data on various subjects and create the objects you need.