There exist many unix/linux commands that are essentially operators in DBMS. In a simple DBMS, what do we really need? Some join, some projection, selection, and sorting. By combining them together, we can build a simple DBMS for text data. Some links to use, 1, 2, 3.

Right now I want to answer the simplest question:

select * from some_file;

So I have to make up some rules:

  • column can be a number or alias:number, where alias is a-z by default or defined using AS.