I'm trying to make a table in which I can generate a column value based on another column value.

For instance:

temp_id column's value should be set automatically like ('temp' id) based on id's value of that row.

I tried to go through this example but was unable to achieve my goal.

CodePudding user response：

You can use a generated column:

create table the_table 
(
  id int primary key generated always as identity,
  temp_id text generated always as ('temp'||id::text) stored,
  "desc" text
);

But why store this at all? A view that returns that expression would be more efficient.

CodePudding user response：

Usually, in such cases, it is not necessary to update any field, it is enough to generate and display this field every time you write select.

select *, 'temp' || id::text as temp_id from table

Or you can create view only one time and use this anytime anywhere:

create view tableview as 
select *, 'temp' || id::text as temp_id from table;

select * from tableview;

If you need this field only in table then you can use generate always field for during creating this table.