Guide to Create Calendar Table with Date Dimensions in Snowflake

A Calendar Table, also known as a Date Dimension Table, is a specialized table in a database that contains a comprehensive list of dates with associated attributes and information. It’s a commonly used approach in data warehousing and analytics to support time-based analysis and reporting. The primary purpose of a calendar table is to provide a structured and standardized way to store and manage date-related data for use in queries, reporting, and analysis.

Benefits of using Calendar Table —

1. Performance: Calendar tables can significantly speed up queries involving time-based calculations and filtering, as the required date attributes are already available.
2. Consistency: Data quality and consistency are improved as date-related attributes are standardized and stored in a single location.
3. Simplicity: Complex date calculations are simplified by referencing pre-calculated attributes from the calendar table.
4. Flexibility: Calendar tables support various time-based analysis scenarios, including trend analysis, period-over-period comparisons, and rolling averages.

In Snowflake, we can build our own calendar table based on Enterprise needs to reap the benefits of it.

Here let us generate 10 years of calendar data that includes previous 5 years, current year and coming 4 years. Following it, based on the Date Column let us derive various Date attributes related to date such as day of the week, day of the month, month, quarter, year, etc., as separate columns.

WITH RECURSIVE CalendarDates AS (
SELECT DATEFROMPARTS(YEAR(CURRENT_DATE) — 5, 1, 1) AS calendar_date
UNION ALL
SELECT DATEADD(DAY, 1, calendar_date)
FROM CalendarDates
WHERE calendar_date < DATEADD(YEAR, 5, DATEFROMPARTS(YEAR(CURRENT_DATE), 1, 1)) — 1
)
SELECT
calendar_date AS DATE
,YEAR(calendar_date) AS YEAR
,MONTH(calendar_date) AS MONTH
,MONTHNAME(calendar_date) AS MONTHNAME
,DAY(calendar_date) AS DAY
,DAYNAME(calendar_date) AS DAYNAME
,QUARTER(calendar_date) AS QUARTER
,WEEK(calendar_date) AS WEEK

,DAYOFMONTH(calendar_date) AS DAYOFMONTH
,DAYOFWEEK(calendar_date) AS DAYOFWEEK
,DAYOFYEAR(calendar_date) AS DAYOFYEAR

,LAST_DAY (calendar_date) AS LAST_DAY_OF_MONTH
,LAST_DAY (calendar_date, ‘QUARTER’) AS LAST_DAY_OF_QUARTER
,LAST_DAY (calendar_date, ‘YEAR’) AS LAST_DAY_OF_YEAR
,LAST_DAY (calendar_date, ‘WEEK’) AS LAST_DAY_OF_WEEK

,WEEKOFYEAR(calendar_date) AS WEEKOFYEAR
,YEAROFWEEK(calendar_date) AS YEAROFWEEK
,YEAROFWEEKISO(calendar_date) AS YEAROFWEEKISO
,WEEKISO(calendar_date) AS WEEKISO
,DAYOFWEEKISO(calendar_date) AS DAYOFWEEKISO

,CEIL(DAYOFMONTH(calendar_date)/7) AS WEEK_OF_MONTH

,CASE
WHEN QUARTER(calendar_date) = 1 THEN DATEFROMPARTS(YEAR(calendar_date), 1, 1)
WHEN QUARTER(calendar_date) = 2 THEN DATEFROMPARTS(YEAR(calendar_date), 4, 1)
WHEN QUARTER(calendar_date) = 3 THEN DATEFROMPARTS(YEAR(calendar_date), 7, 1)
ELSE DATEFROMPARTS(YEAR(calendar_date), 10, 1)
END AS FIRST_DAY_OF_QUARTER
,DATEDIFF (DAY, FIRST_DAY_OF_QUARTER, DATE) + 1 AS DAY_OF_QUARTER
,DATEDIFF (DAY, FIRST_DAY_OF_QUARTER, LAST_DAY_OF_QUARTER) + 1 AS DAYS_IN_QUARTER
,CEIL(DAY_OF_QUARTER/7) AS WEEK_OF_QUARTER

FROM CalendarDates;

Snowflake Wiki Calendar Table Date Dimension Data

A calendar table is a foundational element for time-based analysis in data warehousing and analytics, providing a standardized and efficient way to work with dates and time intervals.

You can customize your calendar table using my reference query where I derived the attributes based on the snowflake community questions and do let me know in comments if you need me to help you with more such date attributes.

References: https://docs.snowflake.com/en/sql-reference/functions-date-time

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