This is the implementation of a very simple database modeled after SQLite. It consists of a single table, where the attributes of a row are an id, username and email, where the only real constraint is that the ID must be non-negative.

First, cd into the SQLite folder in the main repo. When you list out the current directory's contents via ls, you should see the src, include, and spec folders. spec is for testing, using a Ruby file, but we'll get to that later. include contains a header file, which contains constants and definitions for the file in src. Speaking of which...

To run the database, compile it by running gcc db -o src/db.c. This will create an executable called db in the current directory. Then, run it with ./db test, where "test" is an arbitrary name for the name of our database. As you interact with the database, inserted information will be stored in a document called test.

The database has even fewer commands than SQLite. The only actual commands are insert and select``.

For example, insert 1 user1 [email protected] adds a row with id = 1, username = user1, and email = [email protected]. Try messing with the constraints, such as attempting to store too few or too many attributes or a negative id, to verify that they are properly implemented.

Then, the contents of the database can be displayed by querying a select. There are no parameters for select, as it simply outputs the entire content of the table.

This database also supports a few meta commands, which are not formal queries but still yield speciifc outputs. An example of a meta command that SQLite uses is .tables or .schema. The meta commands available are:

• .exit: self-explanatory. Since we use an external file to store the table, running .exit does not delete information that has been inserted previously.'
• .btree: indexes and tables in SQLite use B-trees to store data for logarithmic time operations. Running .btree outputs a visual representation of the data currently stored. More information on B-trees can be found in notes.pdf.
• .constants: This prints out some relevant constant values, such as row size, the cell size of a leaf node, and more.

In the spec folder, there is a db_spec.rb file that contains 13 test cases that verify the database can run the basic commands and meta commands with expected outputs. Once your current directory is SQLite and you have compiled src/db.c, you can run the test cases with rspec spec/db_spec.rb.

A notes.pdf page can be found in the main directory, including an SQLite overview, visual representations, and references.