Exception handling (BEGIN-EXCEPTION-END) in PostgreSQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the BEGIN-EXCEPTION-END block in PostgreSQL?

It is used to handle errors gracefully by running code that might fail inside BEGIN, catching errors in EXCEPTION, and then continuing or cleaning up in END.

intermediate

How do you catch a specific error in a PostgreSQL exception block?

Use WHEN followed by the error name or SQLSTATE code inside the EXCEPTION block to catch specific errors.

beginner

What happens if an error occurs inside a BEGIN block but there is no EXCEPTION block?

The error will stop the transaction and the error will be returned to the caller without any special handling.

intermediate

Write a simple example of a BEGIN-EXCEPTION-END block that catches division by zero error.

BEGIN PERFORM 1 / 0; EXCEPTION WHEN division_by_zero THEN RAISE NOTICE 'Cannot divide by zero'; END;

intermediate

Can you re-raise an error inside the EXCEPTION block in PostgreSQL?

Yes, you can use RAISE to re-throw the error after handling or logging it.

What keyword starts the block where you handle exceptions in PostgreSQL?

A BEGIN

B EXCEPTION

C TRY

D CATCH

The BEGIN keyword starts the block where you write code that might raise exceptions.

Which keyword is used to catch errors in PostgreSQL exception handling?

A CATCH

B EXCEPTION

C HANDLE

D WHEN

Inside the EXCEPTION block, WHEN is used to specify which errors to catch.

What happens if an error is not caught inside a BEGIN-EXCEPTION-END block?

A The transaction continues normally

B The error is propagated and stops the transaction

C The error is ignored

D The error is automatically fixed

If an error is not caught, it propagates and usually stops the transaction.

How do you handle a division by zero error in PostgreSQL exception block?

A WHEN div_zero THEN

B WHEN zero_division THEN

C WHEN division_by_zero THEN

D WHEN divide_by_zero THEN

The correct error name is division_by_zero.

Can you re-raise an error inside the EXCEPTION block?

A Yes, using RAISE

B Yes, using THROW

C No, errors cannot be re-raised

D Only in PL/pgSQL functions

You can re-raise errors using the RAISE statement.

Explain how the BEGIN-EXCEPTION-END block works in PostgreSQL for error handling.

Think about how you try something, catch problems, and then finish.

Describe how to catch and handle a specific error like division by zero in PostgreSQL.

Focus on the keywords and error name.