SQL Tutorial: What is SQL?
SQL, or Structured Query Language, is a programming language designed for managing data in databases. SQL is used to insert, update, delete and retrieve data from a database. It provides a simple and efficient way to interact with the database and perform data manipulation.
Syntax
SQL has a very simple syntax. It includes several keywords such as SELECT, INSERT, UPDATE, DELETE which can be combined with other keywords and clauses to retrieve and store data in a database. Here is an example syntax for the SELECT statement:
SELECT column1, column2, ...
FROM table_name
WHERE condition;
In this example, column1 and column2 are the columns we want to select from the table. table_name is the name of the table where the data is stored. The WHERE clause is used to filter the data based on a condition.
Example
Let's say we have a table named employees with the following data:
| ID | Name | Age | Salary |
|---|---|---|---|
| 1 | John | 25 | 5000 |
| 2 | Jane | 30 | 7000 |
| 3 | Tom | 35 | 9000 |
| 4 | Samantha | 28 | 6000 |
To select the name and salary of employees who have a salary greater than 6000, we would use the following SQL statement:
SELECT Name, Salary
FROM employees
WHERE Salary > 6000;
Output
The output of the previous example would be:
| Name | Salary |
|---|---|
| Jane | 7000 |
| Tom | 9000 |
Explanation
The SELECT statement is used to retrieve the Name and Salary columns from the employees table. The WHERE clause is used to filter the data so that we only get employees with a salary greater than 6000.
Use
SQL is used in a variety of applications, from managing online stores to bank transactions and data warehousing. It is a standard language used by most relational database management systems (RDBMS) like MySQL, Oracle, Microsoft SQL Server, and PostgreSQL.
Important Points
- SQL is a programming language for managing data in databases.
- It includes keywords like SELECT, INSERT, DELETE, and UPDATE to manipulate data.
- The syntax is simple and readable.
- SQL is used in a variety of applications and is compatible with most RDBMS.
Summary
SQL is a powerful language for managing data in databases. It provides a simple and efficient way to interact with the database and perform data manipulation. Whether you are building a new application or managing an existing one, SQL is an essential skill for data management and analysis.