FAQ: PostgreSQL Constraints - Check Constraints Continued

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This community-built FAQ covers the “Check Constraints Continued” exercise from the lesson “PostgreSQL Constraints”.

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This exercise can be found in the following Codecademy content:

Design Databases With PostgreSQL

FAQs on the exercise Check Constraints Continued

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Hi there,

I was going through the first exercise for this topic and noticed confusing instructions. The question asks for values for years_in_role between 0 and 100 but, in fact, the correct answer is to check if the value is higher than 0 and lower than 100. After I’ve read the instructions I used the function ‘BETWEEN’ which was marked incorrect.

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3

Hello! In the exercise:

Using one CHECK statement, write an ALTER TABLE statement that adds a constraint on speakers to ensure that values for years_in_role between 0 and 100.

I replied:

ALTER TABLE speakers
ADD CONSTRAINT chk_years_in_role_range
CHECK (years_in_role >= 0 AND years_in_role <= 100);

but the actual answer is:

ALTER TABLE speakers
ADD CHECK (years_in_role < 100 AND years_in_role > 0);

  • My response specifies a range for years_in_role from 0 to 100, inclusive. This means that years_in_role can be 0, 100, or any number in between.
  • Your statement specifies a range for years_in_role from greater than 0 to less than 100. This means that years_in_role can be any number greater than 0 and less than 100, but cannot be exactly 0 or 100.