Using SQL

SQL code is written as a series of statements. Later in the text, Chapter 5 and Chapter 6 cover statements like CREATE for defining new tables and INSERT for adding data. In this part, Chapter 3 covers SELECT statements, which are arguably the most useful statements for data scientists. SELECT statements are also called queries because they query table(s), with particular characteristics, from databases.

A query is made up of clauses. Every query must have a SELECT and FROM clause. Other clauses include WHERE, GROUP BY, HAVING, and ORDER BY, all of which will be covered in Chapter 3.

Because of the efficiency of data storage in SQL databases, it is often necessary to combine information held across two or more tables. Chapter 4 covers combining tables via JOIN (combining columns) and via UNION (combining rows).