SQL Select Statement
The SELECT statement in SQL is used to retrieve data from a database table.
We can use the SELECT statement to get data from the specified column(s) or all the columns.
SQL SELECT Syntax
The SELECT statement has the following syntax:
SELECT column1, column2, ...
FROM table_name;
SQL SELECT Statement Examples
Suppose we have a table called “Employees” with the following data:
+------------+-----------+----------+------------+
| EmployeeID | FirstName | LastName | Department |
+------------+-----------+----------+------------+
| 1 | Mark | Otto | Finance |
| 2 | Jacob | Thornton | IT |
| 3 | Su | Bird | Marketing |
| 4 | Sam | Burger | IT |
+------------+-----------+----------+------------+
SELECT From a Column
To select “Department” column from the “Employees” table:
SELECT Department FROM Employees;
Output:
+------------+
| Department |
+------------+
| Finance |
| IT |
| Marketing |
| IT |
+------------+
SELECT From Multiple Columns
To select “Department” and “EmployeeID” columns from the “Employees” table:
SELECT EmployeeID, Department FROM Employees;
Output:
+------------+------------+
| EmployeeID | Department |
+------------+------------+
| 1 | Finance |
| 2 | IT |
| 3 | Marketing |
| 4 | IT |
+------------+------------+
SELECT * Statement
To select all the columns from the “Employees” table:
SELECT * FROM Employees;
Output:
+------------+-----------+----------+------------+
| EmployeeID | FirstName | LastName | Department |
+------------+-----------+----------+------------+
| 1 | Mark | Otto | Finance |
| 2 | Jacob | Thornton | IT |
| 3 | Su | Bird | Marketing |
| 4 | Sam | Burger | IT |
+------------+-----------+----------+------------+
Filter Results Using WHERE Clause
We can filter the results from a SELECT query by using the WHERE clause.
For example, to select all employees in the “IT Department” use:
SELECT * FROM Employees WHERE Department='IT'
Output:
+------------+-----------+----------+------------+
| EmployeeID | FirstName | LastName | Department |
+------------+-----------+----------+------------+
| 2 | Jacob | Thornton | IT |
| 4 | Sam | Burger | IT |
+------------+-----------+----------+------------+
Likewise, to select all employee Ids who are in the “IT Department” we use:
SELECT EmployeeID FROM Employees WHERE Department='IT'
Output:
+------------+
| EmployeeID |
+------------+
| 2 |
| 4 |
+------------+