Range types (int4range, daterange) in PostgreSQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Output of int4range containment check

What is the output of this query?

SELECT int4range(1, 5) @> 3 AS contains_three;

PostgreSQL

SELECT int4range(1, 5) @> 3 AS contains_three;

A true

B SyntaxError

C false

D null

💡 Hint

The operator @> checks if the range contains the value.

The range int4range(1,5) includes integers from 1 up to but not including 5. Since 3 is within this range, the result is true.

❓ query_result

intermediate

Result of daterange union operation

What is the result of this query?

SELECT daterange('2023-01-01', '2023-01-10') + daterange('2023-01-05', '2023-01-15') AS union_range;

PostgreSQL

SELECT daterange('2023-01-01', '2023-01-10') + daterange('2023-01-05', '2023-01-15') AS union_range;

A SyntaxError

B '[2023-01-01,2023-01-10)'

C '[2023-01-05,2023-01-15)'

D '[2023-01-01,2023-01-15)'

💡 Hint

The + operator merges overlapping or adjacent ranges.

The two dateranges overlap between 2023-01-05 and 2023-01-10, so their union is a single continuous range from 2023-01-01 to 2023-01-15 (excluding the end).

📝 Syntax

advanced

Identify the syntax error in int4range creation

Which option contains a syntax error when creating an int4range?

Query example: SELECT int4range(...);

A int4range(1, 5, '[]')

B int4range(1, 5, '[)')

C int4range(5, 1)

D )')[' ,5 ,1(egnar4tni

💡 Hint

The lower bound must be less than or equal to the upper bound.

int4range(5, 1) is invalid because the lower bound (5) is greater than the upper bound (1), causing a runtime error.

🔧 Debug

advanced

Why does this daterange overlap query return no rows?

Given a table events(date_range daterange), why does this query return no rows?

SELECT * FROM events WHERE daterange('2023-01-01', '2023-01-10') && daterange('2023-01-10', '2023-01-20');

A The ranges do not overlap because the first ends exactly at the start of the second, and ranges are half-open by default.

B The query syntax is invalid and causes no rows to be returned.

C The && operator checks for containment, not overlap.

D The daterange values are stored as text, so the operator fails silently.

💡 Hint

Remember how half-open ranges treat their boundaries.

By default, dateranges are half-open [start, end), so the first range ends at 2023-01-10 but does not include it, and the second starts at 2023-01-10. They do not overlap, so the && operator returns false.

🧠 Conceptual

expert

Choosing the correct range type for a date interval with inclusive end

You want to store a date interval that includes both the start and end dates (inclusive). Which range type and bounds option should you use in PostgreSQL?

A Use int4range with bounds '[)' and convert dates to integers.

B Use daterange with bounds '[]' to include both start and end dates.

C Use daterange with bounds '(]' to include only the end date.

D Use tsrange with default bounds '[)' for inclusive start and exclusive end.

💡 Hint

Check how bounds affect inclusion of start and end in ranges.

The daterange type with bounds '[]' includes both the start and end dates, making it suitable for fully inclusive date intervals.

Practice

1. What does the PostgreSQL int4range data type store?

easy

A. A range of 4-byte floating point numbers

B. A range of 4-byte integers

C. A range of dates

D. A range of text strings

Solution

1. Step 1: Understand the name int4range

   The prefix int4 means 4-byte integer in PostgreSQL.

2. Step 2: Identify the stored data type

   int4range stores a range (interval) of 4-byte integers.

3. Final Answer:

   A range of 4-byte integers -> Option B

4. Quick Check:

   int4range = integer range [OK]

Hint: Remember int4 means 4-byte integer range [OK]

Common Mistakes:

• Confusing int4range with floating point ranges
• Thinking it stores dates instead of integers
• Assuming it stores text ranges

2. Which of the following is the correct syntax to create a table with a column named period of type daterange?

easy

A. CREATE TABLE events (period daterange[]);

B. CREATE TABLE events (period range(daterange));

C. CREATE TABLE events (period daterange);

D. CREATE TABLE events (period date range);

Solution

1. Step 1: Recall correct type declaration

   In PostgreSQL, range types like daterange are used directly as column types.

2. Step 2: Check each option

   CREATE TABLE events (period daterange); uses period daterange which is correct syntax. CREATE TABLE events (period range(daterange)); wrongly uses range(daterange). CREATE TABLE events (period date range); splits the type incorrectly. CREATE TABLE events (period daterange[]); declares an array, not a single range.

3. Final Answer:

   CREATE TABLE events (period daterange); -> Option C

4. Quick Check:

   Use type name directly for range columns [OK]

Hint: Use range type name directly as column type [OK]

Common Mistakes:

• Adding extra parentheses around range type
• Splitting type name into two words
• Using array syntax when not needed

3. Given the table bookings with a daterange column stay, what does this query return?

SELECT * FROM bookings WHERE stay && daterange('2024-06-01', '2024-06-10');

medium

A. Rows where stay starts exactly on June 1, 2024

B. Rows where stay is completely inside June 1 to June 10, 2024

C. Rows where stay ends before June 10, 2024

D. Rows where stay overlaps with June 1 to June 10, 2024

Solution

1. Step 1: Understand the operator && for ranges

   The && operator checks if two ranges overlap at all.

2. Step 2: Analyze the query condition

   The query selects rows where the stay range overlaps with the range from June 1 to June 10, 2024.

3. Final Answer:

   Rows where stay overlaps with June 1 to June 10, 2024 -> Option D

4. Quick Check:

   Range overlap operator && means any overlap [OK]

Hint: && means any overlap between ranges [OK]

Common Mistakes:

• Thinking && means fully inside
• Confusing overlap with exact start or end match
• Assuming it filters only before or after dates

4. You wrote this query to find bookings fully inside June 2024:

SELECT * FROM bookings WHERE stay <@ daterange('2024-06-01', '2024-06-30');

But it returns no rows even though some bookings are inside June. What is the likely problem?

medium

A. The daterange upper bound is exclusive by default, so '2024-06-30' is not included

B. The <@ operator checks for overlap, not containment

C. The stay column is not of type daterange

D. The query syntax is invalid and causes an error

Solution

1. Step 1: Understand <@ operator meaning

   <@ means the left range is fully contained inside the right range.

2. Step 2: Check daterange bounds behavior

   By default, daterange upper bound is exclusive, so '2024-06-30' is not included in the range. This excludes bookings on June 30.

3. Final Answer:

   The daterange upper bound is exclusive by default, so '2024-06-30' is not included -> Option A

4. Quick Check:

   Upper bound exclusive means end date not included [OK]

Hint: Remember daterange upper bound is exclusive by default [OK]

Common Mistakes:

• Confusing <@ with overlap operator
• Assuming inclusive upper bound by default
• Ignoring data type mismatch

5. You want to find all integer ranges in a table intervals with column int_range (type int4range) that do NOT overlap with [10, 20). Which query correctly finds these non-overlapping ranges?

hard

A. SELECT * FROM intervals WHERE NOT (int_range && int4range(10, 20));

B. SELECT * FROM intervals WHERE int_range && int4range(10, 20);

C. SELECT * FROM intervals WHERE int_range <@ int4range(10, 20);

D. SELECT * FROM intervals WHERE int_range @> int4range(10, 20);

Solution

1. Step 1: Understand the overlap operator &&

   && returns true if ranges overlap.

2. Step 2: Find non-overlapping ranges

   To find ranges that do NOT overlap, negate the overlap condition with NOT (int_range && int4range(10, 20)).

3. Final Answer:

   SELECT * FROM intervals WHERE NOT (int_range && int4range(10, 20)); -> Option A

4. Quick Check:

   Negate overlap to find non-overlapping ranges [OK]

Hint: Use NOT with && to find non-overlapping ranges [OK]

Common Mistakes:

• Using && without NOT to find non-overlapping
• Confusing <@ and @> operators
• Using containment instead of overlap