使用 TeraData SQL 计算任期

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I have been having the hardest time converting this T-SQL to TeraData SQL. Can someone assist me with this. I would really appriecate it. I am not understanding the convertion of dates with teradata. I am super confused.

A fiscal Month example: Starts: 2020-22-01 - Ends: 2020-21-01 This query delivers a data result within the fiscal month of with they started there position. Example: 8/21/2019

   ,CASE WHEN DAY(POSITION_START_DT) BETWEEN 22 AND 31 
         THEN CAST(
               CONCAT(
               CAST(YEAR(POSITION_START_DT)AS VARCHAR(4)),
               CASE WHEN LEN(MONTH(POSITION_START_DT)) = 1 THEN '-0' ELSE '-'END,
               CAST(MONTH(POSITION_START_DT)AS VARCHAR(2)),
               '-21') 
               AS date)

          WHEN DAY(POSITION_START_DT) BETWEEN 1 AND 6 
          THEN CAST(
               CONCAT(
               CAST(YEAR(DATEADD(MONTH,-1,POSITION_START_DT))AS VARCHAR(4)),
               CASE WHEN LEN(MONTH(DATEADD(MONTH,-1,POSITION_START_DT))) = 1 THEN '-0' ELSE '-'END,
               CAST(MONTH(DATEADD(MONTH,-1,POSITION_START_DT))AS VARCHAR(2)),
               '-21') 
           AS date) 

         ELSE CAST(
               CONCAT(
                   CAST(YEAR(DATEADD(MONTH,0,POSITION_START_DT))AS VARCHAR(4)),
                   CASE WHEN LEN(MONTH(DATEADD(MONTH,0,POSITION_START_DT))) = 1 THEN '-0' ELSE '-'END,
                   CAST(MONTH(DATEADD(MONTH,0,POSITION_START_DT))AS VARCHAR(2)),
                   '-21')
               AS date) END AS FISCAL_START_MONTH_INSALES

Fiscal Tenure Bucket uses "Fiscal_Start_Month_insales field and groups the employee in a bucket. Buckets: - 0_3_MONTHS - 4_6_MONTHS - 7_12_MONTHS - 13_24_MONTHS - 25_PLUS_MONTHS - ELSE Unknown

    ,CASE  WHEN DATEDIFF(Day,FiscalStartMonthInSales,CURRENT_DATE)/30  >= 25 THEN '25_PLUS_MONTHS'
                       WHEN DATEDIFF(Day,FiscalStartMonthInSales,CURRENT_DATE)/30  BETWEEN 13 AND 24 THEN '13_24_MONTHS'
                       WHEN DATEDIFF(Day,FiscalStartMonthInSales,CURRENT_DATE)/30  BETWEEN 7 AND 12 THEN '7_12_MONTHS'
                       WHEN DATEDIFF(Day,FiscalStartMonthInSales,CURRENT_DATE)/30  BETWEEN 4 AND 6 THEN '4_6_MONTHS'
                       WHEN DATEDIFF(Day,FiscalStartMonthInSales,CURRENT_DATE)/30  BETWEEN 0 AND 3 THEN '0_3_MONTHS'
                       ELSE 'Unknown' END as PositionTenureBucket

Cheers~ Arron

Answer 1

Just converting functions (and combining the two cases that seem to give identical results), it seems the first part could be

CASE WHEN EXTRACT(DAY FROM POSITION_START_DT) BETWEEN 1 AND 6
     THEN CAST(CAST(CAST(ADD_MONTHS(POSITION_START_DT,-1) AS FORMAT 'YYYY-MM') AS VARCHAR(7))||'-21' AS DATE FORMAT 'YYYY-MM-DD')
     ELSE CAST(CAST(CAST(POSITION_START_DT AS FORMAT 'YYYY-MM') AS VARCHAR(7))||'-21' AS DATE FORMAT 'YYYY-MM-DD')
     END AS FISCAL_START_MONTH_INSALES

And perhaps the second part is just

 ,CASE WHEN (CURRENT_DATE-FiscalStartMonthInSales)/30  >= 25 THEN '25_PLUS_MONTHS'
       WHEN (CURRENT_DATE-FiscalStartMonthInSales)/30   BETWEEN 13 AND 24 THEN '13_24_MONTHS'
       WHEN (CURRENT_DATE-FiscalStartMonthInSales)/30   BETWEEN 7 AND 12 THEN '7_12_MONTHS'
       WHEN (CURRENT_DATE-FiscalStartMonthInSales)/30   BETWEEN 4 AND 6 THEN '4_6_MONTHS'
       WHEN (CURRENT_DATE-FiscalStartMonthInSales)/30   BETWEEN 0 AND 3 THEN '0_3_MONTHS'
       ELSE 'Unknown' END as PositionTenureBucket

Answer 2

Simplifying Fred's first part to:

Cast(To_Char(CASE WHEN Extract(DAY From POSITION_START_DT) BETWEEN 1 AND 6 
                  THEN Add_Months(POSITION_START_DT,-1)
                  ELSE POSITION_START_DT
             END, 'yyyy-mm') || '-21' AS DATE) 

And simplifying the logic to subtract 6 days, get the 1st of the month and add 20 days :

Trunc(POSITION_START_DT - 6, 'mon') + 20