Archive Database Step 1: Read the Schema

Before writing any query, write down the schema of the teaching database by hand: the tables, their columns, the types, and which columns point at which. Then find the three places where a value could be missing and note what a missing value would mean in each. You will use that list in module 4, and the habit of reading a schema before querying it is the one that separates a confident query from a hopeful one.