SQL-Help : a Tutorial to SQL

This is an attempt to introduce you to SQL and to explain what relational databases are, what the relational data model is and how you can extract data from databases with SQL. There are german and russian versions of this page too.

Table of Contents

1.  Preface and warranty statement
2.  SQL-Keywords alphabetically sorted
3.  Common information and definitions in this SQL-help
   • Used syntax
   • SQL language elements in the syntax diagrams
   • Tables used in examples
4.  Basic SQL commands
   • CREATE TABLE - create a database table
   • DELETE FROM - delete records from a table
   • DROP TABLE - delete a database table
   • INSERT - insert records into a table
   • SELECT - select data from a database
   • CASE - command
   • UPDATE - update the data in the records of a table
5.  SQL commands for data extraction support
6.  Other SQL commands
7.  SQL-operators
8.  SQL functions
   • Data aggregation functions in SQL, such as COUNT, SUM ...
   • Mathematical functions in SQL, such as FLOOR, MOD ...
   • String functions in SQL, such as LEFT, SUBSTR ...
   • Date and time functions in SQL, such as WEEKDAY, DATE ...
   • Other functions in SQL, such as NVL
9.  Joining tables in SQL
   • Outer-Joins
10.  Links to software manyfacturers documentation
11.  Copyright statement