Understanding the Problem

As a data analyst, you have a table called DateDimension that contains daily dates starting from 2000-01-01 and ending at 2020-12-31. You want to create a new column called ToY in this table that will contain specific values based on certain conditions related to the date.

The Problem Statement

The problem statement is as follows: you want to create a column ToY that contains values like ‘ToY xx-yy’ where xx is the lower limit year and yy is the upper limit year. This value should be added if the date falls within 01 November of that year and 31 October of the next year.

For example, dates falling between 2018-11-01 and 2019-10-31 will have values like ‘ToY 18-19’ in this new column.

A Closer Look at the Problem

Let’s break down the problem statement:

• The DateDimension table contains daily dates starting from 2000-01-01 to 2020-12-31.
• We want to create a new column called ToY that will contain specific values based on certain conditions related to the date.
• The value in the ToY column should be ‘ToY xx-yy’ where xx is the lower limit year and yy is the upper limit year.

An Alternative Approach

The provided answer suggests using a view instead of adding a new column directly to the table. This approach involves creating a derived table that includes the desired dates, then joining this table with the DateDimension table on the date range.

with dates as (
  select '1999-11-01' as FromDate,'2000-10-31' as ToDate
  Union all
  select '2000-11-01' as FromDate,'2001-10-31' as ToDate
  Union all
  -- Add more dates here...
)
SELECT 
    [DateKey]
      ,[PK_Date]
      ,b.FromDate
      ,b.ToDate
      ,'ToY ' + right(cast(year(FromDate) as varchar),2) + '-' +right(cast(Year(ToDate) as varchar),2)  as Toy
      ,[Date_Clean]
      ,[Date_Name]
      ,[Year]
      ,[Year_Name]
      ,[Year_Int]
      ,[Quarter]
      ,[Quarter_Name]
      ,[Month]
      ,[Month_Name]
      ,[Week]
      ,[Week_Name]
      ,[Day_Of_Week]
      ,[Day_Of_Week_Name]
      ,[Day_Of_Year]
      ,[Day_Of_Year_Name]
      ,[Day_Of_Quarter]
      ,[Day_Of_Quarter_Name]
      ,[Day_Of_Month]
      ,[Day_Of_Month_Name]
      ,[Month_Of_Year]
      ,[Month_Of_Year_Name]
      ,[Month_Of_Quarter]
      ,[Month_Of_Quarter_Name]
      ,[Quarter_Of_Year]
      ,[Quarter_Of_Year_Name]
      ,[Date_Filter]
  FROM [LegOgSpass].[dbo].[DimDate] a
  left join dates b on date_clean between b.Fromdate and b.Todate
)

Understanding the Join Condition

The left join condition in this query is based on the date_clean column from the DateDimension table (a) with the FromDate and ToDate columns in the derived table (b). The date_clean column is used to find dates that fall within the specified range.

SQL Server 2012 Limitations

The provided solution assumes that the SQL Server version being used does not support common table expressions (CTEs) or derived tables. However, these features were introduced in SQL Server 2008 and are widely supported in modern versions of the database management system.

If you’re using an earlier version of SQL Server, you may need to use a different approach or upgrade your database management system to take advantage of these newer features.

Conclusion

In this article, we discussed how to create a new column called ToY that will contain specific values based on certain conditions related to the date in the DateDimension table. We also explored alternative approaches and looked into SQL Server limitations.

Last modified on 2024-02-15