This website explains individual SQL commands, and also provides an online SQL interpreter so that users can practice these...
This website explains individual SQL commands, and also provides an online SQL interpreter so that users can practice these commands. If the student enters a valid SQL query, the database generates output. If the query is faulty, the interpreter returns an error message.Students can use data in the permanent tables in the database, and/or can create temporary tables which will remain on the site for a few days. The tutorial is divided into eight lessons. The site also provides Exercises with some of the lessons, and solutions to the exercises. (The solutions are all together for each lesson, so it is possible for students to see the solution for some of the later exercises when checking their answer for an earlier one.)This tutorial is followed by another one that covers more advanced features of SQL.Technical Remarks:Some of the material quite condensed, so this site is not a substitute for a textbook. For example, the tutorial mentions and discusses constraints on input values, but doesn't provide an code example (although this is available in the second tutorial). Even though it mentions the char and varchar data types, it doesn't really explain the distinction between them. The concept of updating by adding a constant to a value is demonstrated, and assigned as an exercise, without any discussion.