Unable to add check constraint in postgresql

Question

I am using postgesql.

I have already created a database and table. However in one of the table I want to add a constraint but it is not working. I wanted to set the value in column is_official to only T or F.

ALTER TABLE countrylanguage
ALTER COLUMN is_official 
ADD CONSTRAINT conchk 
CHECK (is_official IN ('T','F'));

user330315 · Accepted Answer · 2019-01-28 11:50:47Z

3

A check constraint is not defined on a column, but on the table. So the alter column part is invalid when you try to define a check constraint:

ALTER TABLE countrylanguage
  ADD CONSTRAINT conchk CHECK (is_official IN ('T','F'));

However, it would be better to define the column is_official as boolean rather than a text (or varchar) with a check constraint on it to mimic a true boolean column.

answered Jan 28, 2019 at 11:50

user330315

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