PostgreSQL Exam PGCES-02 Topic 8 Question 30 Discussion

Actual exam question for PostgreSQL's PGCES-02 exam

Question #: 30
Topic #: 8

The tables "s1" and "s2" are defined below. The column "id" for tables "s1" and "s2" is of INTEGER type. The column "enable" for table "s1" is of BOOLEAN type, and the column "name" for table "s2" is of TEXT type.

s1: id |

enable

----+--------

1 | t 2 | f

s2: id |

name ----

+------ 1 |

post 2 |

gre 3 |

SQL

The following SQL was executed. Select the correct number of rows in the result. SELECT * FROM s2 WHERE id IN (SELECT id FROM s1);

A1 row

B2 rows

C3 rows

D4 rows

E5 rows

Show Suggested Answer

Suggested Answer: A

by Glenna at Aug 02, 2022, 07:01 AM

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Tanja

1 months ago

Ah, the old 'SQL query with a twist' trick, eh? I bet the exam writers had a field day coming up with this one. Imagine if the tables were named 'table1' and 'table2' instead - the confusion would be off the charts! But hey, at least they kept the column names simple. 'id' and 'name' - no fancy stuff here. Just good old-fashioned SQL goodness.

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Desmond

2 months ago

This is a classic SQL query, but with a twist! I love these types of questions. Let me break it down... The 's1' table has 2 rows, and the 's2' table has 3 rows. The IN clause will only return the rows from 's2' that have an id matching the ids in 's1'. So, the correct answer is B) 2 rows. Easy peasy!

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Sylvia

7 days ago

Exactly, that's why the correct answer is 2 rows.

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Hortencia

28 days ago

So, it will only return 'post' and 'gre' from 's2'.

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Goldie

29 days ago

Yeah, I agree. The query will only return the rows from 's2' that have matching ids in 's1'.

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Lourdes

1 months ago

I think the answer is B) 2 rows.

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Rhea

2 months ago

Hmm, this one's a bit tricky. I'm going to have to carefully examine the data in the tables to figure this out. Ah, I see now! There are 2 rows in 's1' with ids 1 and 2, and the 's2' table has 3 rows with ids 1, 2, and 3. The IN clause will only return the matching rows, so the correct answer is B) 2 rows.

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Annice

2 months ago

Ah, a classic SQL query with a subquery! I just love these types of questions. Let me think this through... The 's1' table has 2 rows, and the 's2' table has 3 rows. The IN clause will only return the rows from 's2' that have an id matching the ids in 's1'. So, the correct answer is B) 2 rows.

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Sheridan

8 days ago

No, it's definitely B) 2 rows.

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Yvonne

17 days ago

I think it's C) 3 rows.

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Sol

28 days ago

I agree, the answer is B) 2 rows.

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Virgilio

3 months ago

The key to this question is understanding the relationship between the two tables. Since the 'id' column in both tables is of INTEGER type, we can use the IN clause to find the matching ids. Given the data in the tables, there are 2 rows in 's1' table, and 3 rows in 's2' table that have matching ids. Therefore, the correct answer is B) 2 rows.

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