What is SQL?
SQL stands for “Structured Query Language”. It is a domain specific language which means it can be used to play with Relational Database only. As the name suggests SQL is used in handling structured data. Structured data is the data that has some specific structure/ format. It can be stored in tables like format or flat files likes CSV and TSV. It is a language used to query tabular data. It is an ANSI standard language used for manipulating, storing and accessing data in a database.
This is a standardized query language for processing data stored in RDBMS (Relational Database Management System).
Before understanding SQL we need to understand RDBMS first. RDBMS or Relational Database Management System is simply a database that stores structured data and there is a relation between the data. It stores data in tabular format. It has column and rows which contains related data entries. Columns are a vertical entity of a table. It contains the attribute of records and rows are the horizontal entity which contains records/data. The intersection of rows and column contains the information of a record with respect to that attribute. Given below is an example of a table.
It is a language used to query over tabular data. Unlike other languages, SQL is a declarative language, one just needs to specify the result that they want to see and submit the query to RDBMS. RDBMS executes the code at the backend and gives the desired output. Whereas in a procedural language we have to tell a computer each and every step to perform in order to get the output. So if you want to select data from the above table you just need to write below query and execute it.
SELECT * FROM CustomerDetail;
A confusion with SQL is the syntax of SQL query. The elements are not executed in the order they are used in the query. Consider selecting data from above CustomerDetail table.
SELECT ID, Name, Age FROM CustomerDetail
WHERE Age > 20
Order By ID DESC;
The above query will select all the records which have an age greater than 20 and display the result by order of ID. The sequence of execution of elements are as follows :
- FROM: In the query FROM clause is executed first. It selects the tables and joins tables to get the base data.
- WHERE: This clause filters the base data. So that there are fewer records in further processing.
- GROUP BY: Group By clause combines rows into groups to perform aggregation.
- HAVING: This clause is used to filter the aggregated data on the basis of the calculated column.
- SELECT: This clause returns the selected records in the format requested by the user.
- ORDER BY: This clause sorts the final data.
So the lexical order and logical order of clauses in a SQL query differ but one needs to take care of these things when the performance comes into the picture. For smaller data retrieval user has to just mention the output he/she expects.
How does SQL make working so easy
The most important feature of SQL which makes it easy to work with is that it hides the complexity of processing. Since it is a declarative language, the programmer just needs to specify the format of output as per the requirement and the server will take care of all the complexity of retrieval and aggregation. So the code to retrieve data from a table will be smaller if written in SQL as compared to code written in any other language.
It deals only with database objects. This is an advantage as well as a limitation of SQL. Because of this, it can be used to handle only structured data. with limited objects and structured data, working is easy in SQL. Even after dealing only with structural data it has more importance than any other programming language and it is easy to learn. This is based on basic relational algebra and tuple calculus. It takes just a few days to learn the basics of SQL. One can also learn this from an online tutorial. But becoming an expert and getting performance related expertise is an altogether different thing in SQL. It will take some time and hands-on experience. It also supports all the mathematical and string functions to modify the data according to need. It has all the features provided in any other programming language. This makes it an easier language to work with.
Every programming language requires to interact with back end database and this has extensibility that it can be integrated into any language. Thus making it easy to work with any other programming language.
Top SQL Companies
Almost every IT company uses a database to store its data and manage it. But big companies that has a large set of data to deal with are the best to explore data. Given below are some of the top IT companies using SQL:
- Tech Mahindra
Various subset of SQL
SQL queries can be categories into 4 main Category:
1. DDL (Data Definition Language)
As the name suggests these types of queries are used to define the structure of data. Like the structure of a table, schema and modify it. Example –
- CREATE: This command is used to create tables, database, schema etc.
- DROP: This command is used to drop tables and other database objects.
- ALTER: This command is used to alter the definition of database objects.
- TRUNCATE: This command is used to remove tables, procedures, views, and other database objects.
- ADD COLUMN: This command is used to add any column to table schema.
- DROP COLUMN: This command is used to drop a column from any table structure.
2. DML (Data Manipulation Language)
This type of queries is used to manipulate data in the database. Example –
- SELECT INTO: This command is used to select data from one table and insert into another table.
- INSERT: This command is used to insert data/records into a table.
- DELETE: This command is used to delete records from the table.
- UPDATE: This command is used to update the value of any record in the database.
3. DCL (Data Control Language)
This category of SQL queries deals with the access rights and permission control of the database. Example –
- GRANT: This command is used to grant access rights on database objects.
- REVOKE: This command is used to withdraw permission from database objects.
4. TCL (Transaction Control Language)
The transaction is a set of commands that perform a specific task on objects in a single unit of execution. So TCL commands deals with transactions in a database. Example –
- COMMIT: This command is used to commits a transaction. Once committed it cannot be rolled back. This means the previous image of the database before running this transaction cannot be retrieved.
- ROLLBACK: Rollback is used to revert the steps in transactions if an error occurs.
- SAVEPOINT: This command sets a savepoint in the transaction to which steps can be rolled back.
- SET TRANSACTION: This command is used to set characteristics of the transaction.
What can you do with SQL
It is mainly used in SQL SERVER MANAGEMENT STUDIO, a tool to manage database and data. It was launched by Microsoft for configuring, managing and administrating all the components of the database. Given below are the main operation one can do with SQL:
1. Create Database
It can be used to create Database and it’s other objects. One can create a table to store data, stored procedure, functions to process data and views to view data. The user can also play around with joining data from different tables and get meaningful output.
2. Access Database
A user can also manage the access rights on the database and its objects using SQL. One can check which user has executed which query and also privilege user has. An administrator can grant and revoke access from a user.
3. Manage Database
Managing data is not an easy task. Especially when it’s important to business and has a huge size. So efficient storage and retrieval of data are important. SQL lets you do that without any hassle.
4. Manipulating Database
These commands help you manipulate your data. Insert data into tables, delete records, update records all can be done easily using SQL commands. A user can also join different tables and have a view on collective data.
5. Website Use
This can also be used with the integration of another programming language. Every programming language has an extension to embed SQL in its code.
Working with SQL
As we know this is a querying language, and it deals with the data stored in the back end. Hence the interface is not so interesting. One won’t get UI to play with colors and designs. There are just tables with columns and rows. But if data really interests you then SQL is the language you must learn. Working with SQL you get to play with data, join tables and performance tuning. You can write some procedure and transactions to perform analysis task and also schedule a job using SQL.
Advantages of SQL
Below are some of the advantages of SQL
1. Requires no coding
This is a declarative language, one just needs to mention the output he/she wants. It has straight forward commands to perform actions like a select, update, delete etc. One does not need to write complex code to retrieve data from a database or manipulate the data.
2. Well defined standard
It is an ANSI standard language. It has been established as a standard language for querying RDBMS.
3. Interactive Language
It is used to communicate with a database and its objects. We can get the output of complex queries within seconds.
4. Manipulating Database
It’s easy to update records in SQL and maintain the integrity of data. The relationship can also be implemented between two tables.
It can be integrated with other languages to connect with database. The SQL query can be embedded in any other programming language used for application development.
Required SQL Skills
Almost in every organization, there is a need for SQL developer. Below are the skills that are in demand:
1. Back-end Developer
Unlike front-end developer who managed the look and feels of a web app, back-end developer has to manage the data show to the user is proper and data updated in the database tables are correct.
2. Database Administrator
A database administrator is someone who managed the database and its objects. DBA is the one who decides on access right of users.
3. Data Analyst
The data analyst is the one who analyzes the data for a meaningful output.
Why should we use SQL
For almost every application data is important. To store and manage we need a database. And to access, use and manipulate that data we need a standard language. SQL is easy to learn a language, use to manage data stored in the database. One can learn the basics of SQL within a few days. It can be embedded in any other programming language. It is easy to code in SQL. Complex queries can be written in few lines of code. Hence SQL should be used for database related tasks.
With the growing importance of data in the present era, the importance and need of someone who can understand and play with data are also increasing. SQL is getting extended to cloud platforms. Now one can query over millions and trillions of records in no time. It is also used in cutting edge technology like data science. Hence deep knowledge of SQL and it’s services can land you up in one the highest paying jobs.
Who is the right audience for learning SQL technologies
Anyone who has an interest in playing with data is the right audience for learning SQL technologies. Someone who enjoys analyzing data and getting something meaningful out of it.
How SQL helps in career growth
Learning SQL might help you land up in hot jobs like data scientist and data analyst. It opens door to cloud platforms as well. Database administrator and database architect are offered attractive pay scales by a reputed organization.
SQL is an old but important language. It provides you the capability to store and manage data. It gives you all the powers to deal with relational data. It’s simple to learn but might get you an attractive job offer from reputed organization.
This has been a guide to What is SQL. Here we discussed the various SQL subsets and top SQL companies with advantage and scope. You can also go through our other suggested articles-