Testing and SQL

Lot of times people ask me that "is it necessary to know SQL to become good software Tester? the answer depends on the type of Software you are going to test. Almost all web applications interact with the databases. So if you are testing any web applications you must be knowing the language to access the database. SQL is a standard computer language for accessing and manipulating databases. If you know the SQL you can play with the database.

For example: you are testing an e-commerce website and you want to when exactly the purchase details are inserted into the main table in the databse? User can add products to the cart and then remove them and do many iterations before hi finally purchases the products. But whatever transactions the user does, the data must be saved somewhere. There will be different tables in database which hold data in different phases. When user completes his shopping then the data will be entered into the main table and you might be using some batch process code to insert this data into the main tables.

There are many such scenarios where you must be knowing SQL and database concepts to play with the database. So, if you are planning to enter into the Software Testing field then I suggest you to get yourself familiar with the RDBMS concepts and SQL language.

SQL Data Manipulation Language (DML)

SQL (Structured Query Language) is a syntax for executing queries. But the SQL language also includes a syntax to update, insert, and delete records.

These query and update commands together form the Data Manipulation Language (DML) part of SQL:

* SELECT - extracts data from a database table
* UPDATE - updates data in a database table
* DELETE - deletes data from a database table
* INSERT INTO - inserts new data into a database tab

SQL Data Definition Language (DDL)

The Data Definition Language (DDL) part of SQL permits database tables to be created or deleted. We can also define indexes (keys), specify links between tables, and impose constraints between database tables.

The most important DDL statements in SQL are:

* CREATE TABLE - creates a new database table
* ALTER TABLE - alters (changes) a database table
* DROP TABLE - deletes a database table
* CREATE INDEX - creates an index (search key)
* DROP INDEX - deletes an index


w3schools is a best place to learn basic SQL language. The tutorial is presented very nicely. If you start reading and understanding one by one it will be very easy for you to understand SQL. The best part about w3schools is that you can write some test queries and execute them while learning. Visit the site to learn more.