SQL is a standard computer language for accessing and manipulating databases. SQL is also known as computer language used to create, modify, retrieve and manipulate data from relational database management systems.
Client Program communicate your intent to the database server by means of queries written in Structured Query Language which known as SQL. Also can known as the language of relational databases.
Why SQL so important?
Just Imagine how horrible life will be if all the database tools like Oracle, MySQL, SQL server had entirely different sets of command to call the data and put the data from the database store.