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A Simple SQL Join Skill Test

Part 2: Answers (note the questions from the test are shown here also)

Let there be two files:

• FILEA with 100 rows with a numeric unique key spanning from 1 to 100.
• FILEB with 10 rows with a numeric unique key spanning from 1 to 10.

TABLEA	TABLEB
1 2 3 . . . . 100	1 2 3 . . . 10

Using the keys above:

3. TABLEA EXCEPTION JOIN TABLEB should yield how many rows?

o Expected answer: 90 rows

4. TABLEB EXCEPTION JOIN TABLEA should yield how many rows?

o Expected answer: 0 rows

5. TABLEA INNER JOIN TABLEB should yield how many rows?
• Expected answer: 10 rows

6. TABLEB INNER JOIN TABLEA should yield how many rows?
• Expected answer: 10 rows

7. TABLEA LEFT OUTER JOIN TABLEB should yield how many rows?
• Expected answer: 100 rows

8. TABLEA LEFT OUTER JOIN TABLEB should yield how many NULL values?
• Expected answer: 90

9. TABLEB LEFT OUTER JOIN TABLEA should yield how many rows?
• Expected answer: 10 rows

1. 8. If TABLEA had a numeric key and TABLEB had numbers in a character field, is there a way to still do the join?

Expected answer: Yes, with a “CAST” operation.

Let there be two files:

• PLANT_TABLE with 10 rows with a numeric unique key spanning from 1 to 10.
• ITEM_TABLE with 3 rows with numeric unique keys 123, 456, 789

PLANT_TABLE	ITEM_TABLE
1 2 3 . . . 10	123 456 789

2. PLANT_TABLE CROSS JOIN ITEM_TABLE would yield how many rows?
• Expected answer: 30 rows

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