Range types (int4range, daterange) in PostgreSQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a range type in PostgreSQL?

A range type in PostgreSQL represents a continuous set of values between a lower and upper bound, such as numbers or dates. It allows easy querying of intervals without storing each value separately.

beginner

What does int4range represent?

int4range is a built-in PostgreSQL range type that stores a range of 4-byte integers (normal integers). It can represent intervals like [1,10) meaning from 1 up to but not including 10.

beginner

How do you create a daterange value for dates from 2023-01-01 to 2023-01-10 inclusive?

You can write: '[2023-01-01,2023-01-10]'::daterange. The square brackets mean the range includes both start and end dates.

intermediate

How can you check if a value is inside a range in PostgreSQL?

Use the @> operator. For example, int4range(1,10) @> 5 returns true because 5 is inside the range 1 to 10.

intermediate

What is the difference between [1,10) and (1,10] in range types?

[1,10) includes 1 but excludes 10. (1,10] excludes 1 but includes 10. Square brackets mean inclusive, parentheses mean exclusive bounds.

Which PostgreSQL range type would you use to store a range of dates?

A daterange

B int4range

C textrange

D numrange

daterange is the correct type for date intervals. int4range is for integers, numrange for numeric ranges, and textrange does not exist.

What does the range notation [5,15) mean?

A Includes 5 and excludes 15

B Excludes 5 and includes 15

C Includes both 5 and 15

D Excludes both 5 and 15

Square bracket [ means inclusive, parenthesis ) means exclusive. So [5,15) includes 5 but excludes 15.

Which operator checks if a range contains a value in PostgreSQL?

A <@

B @>

C &&

D <<

The @> operator tests if the range contains the value. For example, int4range(1,10) @> 5 is true.

How do you cast a string to a range type in PostgreSQL?

A You cannot cast strings to range types

B Use <code>CAST()</code> only

C Use <code>::</code> operator, e.g. <code>'[1,5]'::int4range</code>

D Use <code>TO_RANGE()</code> function

You can cast a string to a range type using ::, like '[1,5]'::int4range.

What will daterange('2023-01-01','2023-01-10', '[]') represent?

A Dates from Jan 2 to Jan 9 inclusive

B Dates from Jan 1 to Jan 10 excluding Jan 10

C Invalid syntax

D Dates from Jan 1 to Jan 10 inclusive

The '[]' means both bounds are inclusive, so the range includes Jan 1 and Jan 10.

Explain what range types are in PostgreSQL and give examples of when you might use int4range and daterange.

Think about intervals like date bookings or number spans.

Describe how to check if a value is inside a range and how to create a range with inclusive or exclusive bounds.

Remember the symbols for inclusive and exclusive bounds.

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