PostgreSQL Exam PGCES-02 Topic 11 Question 38 Discussion

Actual exam question for PostgreSQL's PGCES-02 exam

Question #: 38
Topic #: 11

A table is defined as follows: CREATE TABLE t (id INT, val TEXT); Select two correct statements from below about the function "get_head" defined below. CREATE

FUNCTION get_head(BOOLEAN) RETURNS TEXT LANGUAGE sql CALLED ON

NULL INPUT AS 'SELECT val FROM t WHERE $1 OR id > 0 ORDER BY id LIMIT 1;';

AThis function is defined using PL/pgSQL.

BThere are cases where this function returns multiple lines.

CWhen NULL is passed for the argument and the function is executed, NULL is returned.

DEven if this function is passed the same parameter value and executed multiple times, the returned values will not necessarily also be the same value.

EIf a function with the same name and with type BOOLEAN as the parameter is already defined, an error occurs.

Show Suggested Answer

Suggested Answer: A, D

by Devorah at Jan 09, 2023, 01:14 PM

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Truman

1 days ago

Wait, is this a trick question? What if the table is empty? In that case, the function would return NULL, so C is definitely correct. As for the other statement, I'll go with D - it sounds like it could return different values even with the same parameter.

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Lucille

1 days ago

I agree with statement D because the function might not always return the same value.

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Ashleigh

4 days ago

I'm a bit stumped on this one. Is the function going to return the first row based on the id, or the first row where the condition is true? I guess I'll go with C and D, just to be safe.

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Mollie

4 days ago

I think statement C is correct because if NULL is passed, NULL is returned.

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Glendora

7 days ago

This is a tricky one! I'm going to say B and D are the correct statements. The function could return multiple lines if there are multiple rows with id > 0, and the returned value might change if the table is updated between function calls.

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Vanesa

8 days ago

Hmm, if the function is called with NULL input, it should return NULL, so C is correct. But I'm not sure about the other statement, let me think about it.

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Nohemi

9 days ago

The function is not defined using PL/pgSQL, it's using SQL language. I'm going with C and D.

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