PostgreSQL PGCES-02 Exam - 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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Tennie

7 months ago

Seems like a straightforward query, but I’m surprised by the result!

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Garry

7 months ago

I thought it would be 1 row, but I see the logic now.

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Marvel

7 months ago

Wait, why would it return 3?

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Rosio

7 months ago

Definitely 2 rows!

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Veronique

7 months ago

The subquery returns ids 1 and 2 from s1.

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Marisha

8 months ago

I might be confused, but I feel like the result could also be 1 row if there's something I'm missing about the IDs.

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Brittni

8 months ago

If I recall correctly, the IDs in s1 are 1 and 2, so that should match with s2 and give us 2 rows.

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Benedict

8 months ago

I'm not entirely sure, but I remember something similar where the subquery only returned the IDs that exist in both tables.

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Boris

8 months ago

I think the query will return 2 rows because there are two matching IDs in table s1.

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Boris

8 months ago

Definitely Benchmarking. It's the classic tool for analyzing how your organization stacks up against the competition and identifying areas for improvement.

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Kris

8 months ago

This seems pretty straightforward. The origin attribute is set to incomplete when using the import-route command, so the answer must be TRUE.

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Jerry

8 months ago

This seems straightforward. The loop is displaying the last three values, so the answer must be A.

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Tanja

1 year 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

1 year 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

11 months ago

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

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Hortencia

12 months ago

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

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Goldie

12 months ago

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

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Lourdes

12 months ago

I think the answer is B) 2 rows.

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Rhea

1 year 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

1 year 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

11 months ago

No, it's definitely B) 2 rows.

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Yvonne

11 months ago

I think it's C) 3 rows.

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Sol

12 months ago

I agree, the answer is B) 2 rows.

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Virgilio

1 year 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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