The WHERE Clause
In this lesson, we will learn how to use the WHERE clause in SQL to view specific data from table.
We'll cover the following
The WHERE clause#
The SQL WHERE clause is used to specify a condition while fetching the data from a single table. If the given condition is satisfied, then those specific records are returned from the table.
Syntax#
The basic syntax of the SELECT statement with the WHERE clause is as shown below:
SELECT column1, column2, ... columnN
FROM table_name
WHERE [condition];
You can specify a condition using the comparison or logical operators like >, <, =, LIKE, NOT, etc.
Example #1#
Let’s consider the CUSTOMERS table again.
| ID | NAME | AGE | ADDRESS | SALARY |
|---|---|---|---|---|
| 1 | Mark | 32 | Texas | 50000.00 |
| 2 | John | 25 | NY | 65000.00 |
| 3 | Emily | 23 | Ohio | 20000.00 |
| 4 | Bill | 25 | Chicago | 75000.00 |
| 5 | Tom | 27 | Washington | 35000.00 |
| 6 | Jane | 22 | Texas | 45000.00 |
Let’s say we want to fetch the ID, Name and Salary fields from the CUSTOMERS table, provided that the salary of the customer is greater than $50,000.
So when we write our SQL query, will get the following result:
The following code shows how to do this in SQL:
Example #2#
Let’s consider another query, which would fetch all the fields from the CUSTOMERS table for a customer with the name John.
In this case, our query will produce the following result:
The SQL query is for this problem written below:
Here, it is important to note that all the strings and characters should be inside single quotes (’’), whereas, numeric values should be given without any quotes.
Quick quiz!#
What will be the output of the following query?
SELECT NAME, ADDRESS
FROM CUSTOMERS
WHERE ADDRESS = 'Texas';
A)
| NAME | ADDRESS |
|---|---|
| Mark | Texas |
| John | NY |
| Emily | Ohio |
| Bill | Chicago |
| Tom | Washington |
| Jane | Texas |
B)
| NAME | ADDRESS |
|---|---|
| Mark | Texas |
C)
| NAME | ADDRESS |
|---|---|
| Jane | Texas |
D)
| NAME | ADDRESS |
|---|---|
| Mark | Texas |
| Jane | Texas |
In the next lesson, we will take a look a the AND & OR clause.
