PostgreSQL WHERE NOT EQUAL Clause
Making complex statements in queries when searching for data in tables is a common task. That’s because there are often times when you’ll want to run a second query on the first set of results that were returned. Although it can pose challenging, the good news is that you can do it seamlessly and fast with the handy PostgreSQL syntax WHERE NOT EQUAL clause. Learn how to drill down further and fine-tune the result response. Locate the data you need in record time.
- Download, install, configure, and then run PostgresSQL for your OS.
How to start PostgreSQL in LINUX
- Use the following sudo start command give access permissions and start PostgreSQL on a LINUX OS:
- Use the following status command to confirm PostgreSQL is running:
- You should see a result similar to this one below:
Loaded: loaded (/lib/systemd/system/postgresql.service; enabled; vendor prese
Active: active (exited) since Thu 2019-08-01 14:51:20 PST; 36min ago
Process: 1230 ExecStart=/bin/true (code=exited, status=0/SUCCESS)
Main PID: 1230 (code=exited, status=0/SUCCESS)
Aug 01 14:51:20 user-UX330UAK systemd: Starting PostgreSQL RDBMS...
Aug 01 14:51:20 user-UX330UAK systemd: Started PostgreSQL RDBMS.
lines 1-8/8 (END)
How to start PostgreSQL in Windows
For your Windows-based OS, follow these steps to verify PostgreSQL is running:
- Access the Control Panel
- Go to Administrative Tools
- Select Services
- Locate the PostgreSQL Server
- Start or restart the service if it stopped running.
The purpose of the PostgreSQL Comparison Operator
To compare two assessments, use the PostgreSQL comparison operator symbol. If a
NULL expression is present, it will return an
UNKNOWN response to present invalidity. Otherwise, without
NULL, you’ll get a
A simple example of using the PostgreSQL Where Clause
After you query using an SQL statement, use PostgreSQL Where to get selected data from those results. It’s based on the criteria that you set.
- Here’s an easy example of how to the PostgreSQL WHERE clause script is written:
As shown in the above example, note that the
WHERE clause is implemented after the
SELECT operation’s clause
Specifically, rows returned in the result response from the
SELECT operation are those that were filtered out by the
WHERE clause. Furthermore, the rows that match the condition of
true will show up in the result.
The three options for the condition of the
WHERE results are:
A list of comparison operators
It’s good to know that some statements help to refine the rows affected by comparison operators. For example,
ORDER BY are statements that pair with the
WHERE clause and there are others.
Let’s look at comparison operators now though, which are the refining symbols used with the
WHERE clause for the data to be returned.
Here’s the entire list of comparison operators:
<— Not Equal
>=— Greater Than or Equal
<=— Less Than or Equal
<— Less Than
>— Greater Than
AND— Logical Operator AND
OR— Logical Operator OR
Example of the PostgreSQL WHERE NOT EQUAL combination clause
Here’s how to use the
NOT EQUAL comparison operator with the clause
- First, create a test database sample:
customer_id INT PRIMARY KEY NOT NULL,
firstname TEXT NOT NULL,
lastname TEXT NOT NULL,
email TEXT NOT NULL
- Add some test records like this:
(1, 'Raymond', 'Elizario', 'email@example.com'),
(2, 'Vera', 'Dadula', 'firstname.lastname@example.org'),
(3, 'Raymond', 'Escalona', 'email@example.com');
- Write some queries to test out on the database sample you just created:
- Instead of the comparison operator used above, try
<, another comparison operator of
Take a closer look at the statement shown above as it doesn’t use the Less Than (
<) comparison operator in that example. The operator
!=) is paired with the clause
WHERE. The criteria states to find the customers that do not have the
You should see a result similar to this:
customer_id | firstname | lastname | email
1 | Raymond | Elizario | firstname.lastname@example.org
2 | Vera | Dadula | email@example.com
An example of WHERE clause in PostgreSQL paired with NOT EQUAL comparison operator
- You can use more than one comparison operator with the clause
WHERE. Let’s try it with
NOT EQUALcomparison operators.
The example above illustrates a
SELECTstatement querying the
WHEREclause is looking for first names in the table with specific criteria. It wants returned rows where
firstname, therefore it must be unequal to that name. In addition, those rows where the
lastname, so it is also unequal to that name.
You should see a result close to this one:
3 | Raymond | Escalona | firstname.lastname@example.org
This tutorial showed you how to use PostgreSQL WHERE NOT EQUAL clause. You learned how to use the
WHERE statement along with
FROM to query tables. The list of comparison operators including
!= not equal operators, give you the ability to create complex queries on the data in tables. Experiment with them in your projects to make your querying simpler, more stress-free, and straight to the point.
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