SELECT Statement & DISTINCT Clause
1. What is SELECT Statement?
The SELECT statement is used to retrieve data from a table.
It is the most important and frequently used SQL command.
2. Basic SELECT Syntax
SELECT column_name
FROM table_name;
3. Select All Columns (*)
Fetches all columns from a table.
SELECT * FROM employees;
* means all columns
4. Select Specific Columns
Retrieve only required columns.
SELECT emp_name, salary
FROM employees;
5. Column Aliases (AS)
Used to give temporary names to columns in output.
SELECT emp_name AS Name, salary AS Salary
FROM employees;
Alias without AS:
SELECT emp_name Name, salary Salary
FROM employees;
6. SELECT with Expressions
You can perform calculations inside SELECT.
SELECT emp_name, salary * 12 AS Annual_Salary
FROM employees;
7. DISTINCT Keyword
Used to remove duplicate values from results.
Example Table: employees
| emp_id | emp_name | department |
|---|---|---|
| 1 | Ravi | IT |
| 2 | Priya | HR |
| 3 | Karthik | IT |
| 4 | Anu | HR |
Without DISTINCT:
SELECT department FROM employees;
Result:
IT
HR
IT
HR
With DISTINCT:
SELECT DISTINCT department FROM employees;
Result:
IT
HR
8. DISTINCT with Multiple Columns
Distinct combination of columns.
SELECT DISTINCT department, emp_name
FROM employees;
9. SELECT with ORDER BY (Intro)
SELECT emp_name, salary
FROM employees
ORDER BY salary;
Descending order:
ORDER BY salary DESC;
Top comments (1)
Good luck 🚀