Thursday, 13 March 2014

Oracle for Absolute Beginners: Part 2 - SQL

A wise man* once said, no one’s ever learned how to cook just by reading recipes. And so, since we painted in the background in Part 1, we are now going to roll up our sleeves and dive in. By the end of this article you will be reading and writing SQL, the lingua franca of databases.
[* that wise man was me.]


SQL stands for Structured Query Language (pronounced ess-cue-ell or sequel) and is the programming language used in the management of relational databases. And not just Oracle RDBMS; the code we are about to learn will work just as well with Microsoft’s SQL Server, IBM’s Informix, MySQL and dozens of others. SQL is very much the English of the database world; it is spoken in many environments.  This is one reason why the skills you are about to learn are very valuable; they are eminently transferrable.
SQL consists of a data definition language (DDL) and data manipulation language (DML).  What this means is that we use SQL not only to define the tables into which we plan to put our data, but to manipulate (query, edit, delete, stuff like that) the data once it’s in place.
Manipulating data using SQL is easy, as the syntax isn’t a million miles from the way we speak.  For instance, to select all the data from a table you would use the SELECT … FROM table_name command.  If, on the other hand, you wanted to update data, you’d use the UPDATE command; and the DELETE and INSERT commands pretty much do what you’d expect them to, too.
It’s easy.  Let me show you.

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