When we created the installer, we used the Schema API to define how our new biography content type table looks. However, the Schema API is abstract enough that we wrote no SQL, and we didn't directly call any database functions.
Now we will create four functions that deal with the database at a low level, and we will write SQL statements to perform database operations.
We need to define functions to perform the following:
Insert a new biography entry into the biography table.
Remove an unwanted entry from the biography table.
Update an existing entry in the biography table.
Remove a particular version (or revision) from the biography table.
Keep in mind that the biography table that we created earlier is an auxiliary table. Much of the content type's data is stored in the node table. Only identification information and data that is specific to our content type (like dates, life, and works) is stored in our custom table.
The functions that we define will only need to operate on our...