Want to learn how to compute the value for a Generated Column in PostgreSQL 15.

In this video, we will learn how to use a Generated Column. This special column type, value, is computed from one or more other columns, or other function.
Generated Columns.
Learn how to create a table, that has a column of type GENERATED COLUMN.
Learn how to write insert command on a table that has a GENERATED COLUMN.
Learn how to select data from a table that has a GENERATED COLUMN.
Lastly, how to perform the UPDATE command on a table that has a GENERATED COLUMN.
#softwareNuggets, #postgresql

[@SoftwareNuggets]

Here is the source code for this video:
select version()
show server_version;
drop table HR_Employee
create table HR_Employee
(
emp_id int not null,
annual_salary numeric not null,

--a generated column is a table column
--that is "always generated" from some other column or columns
--the computation must produce the same datatype
hourly_rate numeric generated always as (annual_salary / 2080) stored
)
insert into HR_Employee(emp_id, annual_salary)
values
(1, 35000.00),
(2, 50000.00),
(3, 100000.00);
select *
from HR_Employee
select *
from HR_Employee
where hourly_rate > 20
update HR_Employee
set annual_salary = 55000
where emp_id = 2;

[@LibyaMicro]

Excellent in Firebird databases there are also computed column that can fetch the value of a field from another table. such as bringing the department name from another table with the value of the field ID in the current table

[@SoftwareNuggets]

I need to check out firebird. Thanks for the introduction!!

[@LibyaMicro]

@@SoftwareNuggets However, this can only be done in PostgreSQL by calling a function.
CREATE TABLE product (
product_id UUID
price FLOAT
available_location VARCHAR GENERATED ALWAYS AS fetch_product_location(product_id)
)

[@SoftwareNuggets]

@LibyaMicro that’s a great example. Thanks for the update.

[@downey2294]

what if i wanted to compute the value based on other values in other columns
lets say that i have 2 entities test and semester
and the entity test has a foreign key semester_id and a regular column credit_score
and the entity semester also has credit_score which is the sum of all the credit_score of all the tests that are related to the semester.
how would i compute the credit_score for semester.

[@SoftwareNuggets]

Plz send me your table design and some sample data, and I’ll help you. Send to [e-mail]