Why set operations matter in PostgreSQL - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to combine two tables and remove duplicates.

PostgreSQL

SELECT column_name FROM table1 [1] SELECT column_name FROM table2;

Drag options to blanks, or click blank then click option'

AJOIN

BUNION

CINTERSECT

DEXCEPT

Attempts:

3 left

💡 Hint

Common Mistakes

Using JOIN instead of UNION causes syntax errors.

Using INTERSECT returns only common rows, not all combined.

The UNION operation combines results from two queries and removes duplicates.

2fill in blank

medium

Complete the code to find common rows between two tables.

PostgreSQL

SELECT column_name FROM table1 [1] SELECT column_name FROM table2;

Drag options to blanks, or click blank then click option'

AJOIN

BUNION

CEXCEPT

DINTERSECT

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNION returns all unique rows, not just common ones.

Using EXCEPT returns rows in first query but not second.

The INTERSECT operation returns only rows that appear in both queries.

3fill in blank

hard

Fix the error in the code to find rows in table1 but not in table2.

PostgreSQL

SELECT column_name FROM table1 [1] SELECT column_name FROM table2;

Drag options to blanks, or click blank then click option'

AEXCEPT

BUNION

CINTERSECT

DJOIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using INTERSECT returns common rows, not unique ones.

Using UNION returns all unique rows combined.

The EXCEPT operation returns rows from the first query that are not in the second.

4fill in blank

hard

Complete the code to combine two tables including duplicates.

PostgreSQL

SELECT column_name FROM table1 [1] SELECT column_name FROM table2 ;;

Drag options to blanks, or click blank then click option'

AUNION ALL

BUNION

CINTERSECT

D;

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNION removes duplicates.

Missing semicolon causes syntax errors.

The UNION ALL operation combines results from two queries including duplicates.

5fill in blank

hard

Fill all three blanks to find rows in table1 not in table2 and order results.

PostgreSQL

SELECT column_name FROM table1 [1] SELECT column_name FROM table2 [2] ORDER BY [3];

Drag options to blanks, or click blank then click option'

AEXCEPT

B;

Ccolumn_name

DUNION

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNION returns all unique rows, not just differences.

Forgetting semicolon causes errors.

Ordering by a non-existent column causes errors.

The EXCEPT operation returns rows from the first query that are not in the second. ORDER BY column_name sorts the results.