Any documents which gives the overall idea of sql course?

I assume you are referring to the Beginning SQL Track, and the description can be found on the main track page:

SQL, or structured query language, is an important tool for business analysts, data analysts and data scientists. It's the language used to read, add, update and remove information from relational databases. SQL lets you search, sort, aggregate, and analyze data to create complex reports to help make important business decisions. It's also used by application designers and programmers to modify, add, and delete data from databases. In this track, we'll introduce the basics of the SQL language, how to use it to read information, how to use it to create reports, how to use it for CRUD (create, read, update and delete) operations, and how to create complex queries that join information across multiple tables of data and databases with millions of pieces of information. You'll also learn how to count records, average values, and perform mathematical operations on your data.