What is SQL – Structured Query Language
What is SQL or Structured Query Language becomes easier to understand if we look at database systems first. A database is a repository of data vital to the activities that need large amounts of data to be stored. Businesses are examples of such activities. Usually such data is used again and again. That requires the data to be organized and easily accessible. Retrieval or update of such data is required to be accurate. Relational databases allow users to set up flexible search criteria to accurately locate a specific data item. Relational databases organize data as tables of rows and columns. RDBMS lets users create flexible queries and locate data accurately. Query language offers standardized syntax to specify such queries. When found, operations possible on the data using Structured Query Language are:
- Reading record(s) or parts of them
- Modifying record and store back
- Deleting record(s)
RDBMS or the relational database management systems use SQL programming language. SQL is a standardized form of proprietary query languages used by the product companies. Structured Query Language is a standard of both ANSI and ISO organizations. Standardization makes migrating easier. Substantial changes to the SQL statements used in an application should not be required when moved to another database.
Many of the database products use SQL. Major, well-known database products available are Oracle, IBM DB2, Microsoft SQL Server, etc. Open source MySQL is a very popular product. Structured Query Language available with each of these products offer the core functions. Unfortunately, these companies implement additional functions. The core functions offer select, insert, create, update, delete and drop, etc. These are really sufficient to implement most operations one needs. SQL of these products coupled with the extensions are known differently. T-SQL is offered by Microsoft in SQL Server product while the Oracle version is called PL/SQL.
Distributed database applications, typically, work with a central database server known as the backend. Client applications communicate with this back-end to retrieve data and manipulate them. These clients issue queries for data with Structured Query Language statements. The database server is then updated with the changed data.
SQL is able to change/modify data in the RDBMS. Besides, it is able to change the structure of the database tables. Structured Query Language statements will let a user create a table, modify it or even entirely delete it. What SQL statements can do with data is insert data into fields in the table. What SQL lets you do is to “select” a specific table for modifications. A SQL “update” command changes the value of a piece (field) of data.
If you need to work with RDBMS applications, the core functions that constitute what is SQL would be easy to learn. There are only a few commands that are used. Learning the syntax of how the command word and associated parameters are used is quite simple too. Even when your application needs to migrate to any other RDBMS, it should not be difficult to manage. Optimization can be implemented through the core SQL first, the product specific extensions can be done as a next step.
Further Reading on SQL: