PostgreSQL Update & Delete

PostgreSQL Update & Delete

1. PostgreSQL Update

Revise Row Content

Use the UPDATE command to revise field entries in previously stored rows.

Illustration

Change the paint value of the entry where brand equals 'Volvo':

UPDATE vehicles   
SET paint = 'crimson'   
WHERE maker = 'Volvo';

Effect

UPDATE 1

→ Indicates a single line was changed by this action.

Caution

The WHERE segment limits which lines are altered—without it, multiple or all matches may be modified.

Inspect Output

To view how things changed, run a command to display everything:

SELECT * FROM vehicles;

2. PostgreSQL Delete

Erase Table Entries

The DELETE operation is employed to remove data rows from an existing dataset.

Important Reminder

Use caution when erasing content. The condition following WHERE defines the target entries to eliminate.

If no filtering condition is included, every item in the dataset will be wiped.

Sample Operation

Eliminate any rows where maker is ‘Volvo’:

DELETE FROM autos   
WHERE maker = 'Volvo';

Outcome

DELETE 1

→ Implies one entry has been removed.

View Current Data

Execute the below line to examine the current state of the table:

SELECT * FROM autos;

Clear Entire Dataset

You may strip all content from the table while retaining its blueprint (structure, fields, etc).

Example Removal

Purge the full content from the autos table:

DELETE FROM autos;

Result Shown

DELETE 3

→ Confirms that 3 entries have been purged.

Inspect Again

Use the same fetch command to verify:

SELECT * FROM autos;

Alternative Shortcut

The same outcome can be produced with the TRUNCATE command, which is a faster way to empty the table.

Quick Format

Clear all records from the autos structure:

TRUNCATE TABLE autos;

Result Noted

TRUNCATE TABLE

Final Check

Display what remains (likely nothing):

SELECT * FROM autos;