How to Get all Dates Between Two Dates in SQL

Navigating and manipulating date ranges is a frequent task in SQL, and efficiently extracting all dates between two given dates is a valuable skill.

This article covers two approaches to using the GROUP BY clause: the traditional method with explicit column names and the shorter “GROUP BY 1” syntax. We’ll use a practical example with a table named dates_table to help you understand this topic.

The “GROUP BY 1” syntax is a shorthand method that allows grouping by the first column in the SELECT list. This can be particularly handy when the SELECT list contains only one expression.

dates_table Overview

Let’s first introduce the table we’ll be working with:

Method 1: Traditional “GROUP BY” with Column Names

In this approach, we will use the traditional “GROUP BY” clause with explicit column names.

Syntax:

SELECT column_name, aggregate_function(column_name)

FROM table_name

WHERE condition

GROUP BY column_name;

Example

Let’s say we have a table named dates_table with columns date_id and date_value. We want to retrieve the count of occurrences for each date value.

SELECT date_value, COUNT(date_id) as occurrences
FROM dates_table
WHERE date_value BETWEEN '2022-01-01' AND '2022-01-10'
GROUP BY date_value;

Output:

| date_value | occurrences   |
|------------|------------- |
| 2022-01-01 | 5                        |
| 2022-01-02 | 3                       |
| 2022-01-03 | 8                       |

In this example, we retrieve the count of occurrences for each date value between ‘2022-01-01’ and ‘2022-01-10’. The result provides a clear breakdown of date occurrences.

Explanation:

The SQL query counts the occurrences of each unique ‘date_value‘ within the specified date range from ‘2022-01-01‘ to ‘2022-01-10‘ in the ‘dates_table’. The output includes two columns: ‘date_value’ and ‘occurrences’, showing the count of occurrences for each distinct date within the specified range.

Method 2: Utilising Ordinal Numbers to “GROUP BY 1”

In this approach, we leverage the “GROUP BY 1” syntax for a more concise grouping when there is only one expression in the SELECT list.

Syntax:

SELECT expression, aggregate_function(expression)

FROM table_name

WHERE condition

GROUP BY 1;

Example

Building on the previous example, we can achieve the same result using “GROUP BY 1.”

SELECT date_value, COUNT(date_id) as occurrences
FROM dates_table
WHERE date_value BETWEEN '2022-01-01' AND '2022-01-10'
GROUP BY 1;

Output:

| date_value | occurrences |
|------------|-------------|
| 2022-01-01 | 5           |
| 2022-01-02 | 3           |
| 2022-01-03 | 8           |

In both cases, the output is identical. The “GROUP BY 1” method, however, presents a more streamlined syntax when working with a single expression.

Explanation:

The SQL query counts occurrences of each unique ‘date_value’ within the specified date range from ‘2022-01-01‘ to ‘2022-01-10‘ in the ‘dates_table’. The output includes two columns: ‘date_value‘ and ‘occurrences‘, grouping results by the first column (‘date_value’).

In conclusion, the ability to extract dates between two given dates in SQL is a valuable skill, and the GROUP BY clause plays a pivotal role in achieving this. The traditional and “GROUP BY 1” methods both provide efficient solutions, with the choice between them depending on the specific requirements of the query.