Date range overlap detection in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select all records where the start date is before the end date.

SQL

SELECT * FROM events WHERE start_date [1] end_date;

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

A<

B>=

C=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' reverses the date order.

Using '=' allows zero-length ranges which may not be valid.

The start date should be less than the end date to form a valid date range.

2fill in blank

medium

Complete the code to find overlapping date ranges between two tables on the start date.

SQL

SELECT a.id, b.id FROM bookings a JOIN reservations b ON a.start_date [1] b.end_date;

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

A>

B<

C<=

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' excludes cases where dates touch exactly.

Using '>' misses overlaps where start is before end.

To detect overlap, the start date of one range must be less than or equal to the end date of the other.

3fill in blank

hard

Fix the error in the overlap condition to correctly detect overlapping date ranges.

SQL

SELECT * FROM periods WHERE NOT (period_end [1] period_start2 OR period_end2 [1] period_start);

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

A>

B<=

C<

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' or '>=' reverses the logic and causes wrong results.

Using '<' misses cases where periods touch exactly.

The correct condition uses '<=' to check if one period ends before or at the other starts, meaning no overlap.

4fill in blank

hard

Fill both blanks to complete the query that finds overlapping date ranges between two tables.

SQL

SELECT a.id, b.id FROM events a JOIN events b ON a.start_date [1] b.end_date AND a.end_date [2] b.start_date WHERE a.id != b.id;

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

A<=

B>=

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>=' in the first blank reverses the logic.

Using '<=' in the second blank misses overlaps where dates touch.

Two ranges overlap if a starts before b ends (<) and a ends after b starts (>=).

5fill in blank

hard

Fill all three blanks to write a query that detects overlapping date ranges and selects their IDs.

SQL

SELECT a.[1], b.[2] FROM schedules a JOIN schedules b ON a.[3] < b.end_date AND a.end_date >= b.start_date WHERE a.[1] != b.[2];

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

Aschedule_id

Bid

Cstart_date

Devent_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using different ID columns for a and b causes errors.

Using wrong date columns breaks the overlap logic.

The query compares start_date with end_date to find overlaps and selects schedule_id from both tables.