The data files are 5 denormalized CSV tables. If you want to load the data into a relational database, below are scripts both to help load the data into 5 tables and also to migrate the data into 9 partially normalized tables, which are more suitable for exploration with SQL. The scripts provided are for PostgreSQL, but should be simple to modify for other relational databases.
The entity-relation diagrams (ERDs) below only show keys that would be used for joining/grouping. Full documentation of all the fields in the data files can be found in the documentation for each.
Also, the table names diagrammed are different (and shorter) than the names that are actually used in the scripts as distributed. Simply remove the long (and admittedly unwieldy donorschoose_ and normalized_) prefixes to get the names shown in these ERDs. If you do so, the 5 spreadsheet table names will be in the plural and the 9 partially normalized tables will be in the singular, exactly as shown below.
SQL script to migrate the data from the 5 original tables (above) into 9 partially normalized tables (below).