Is there any way to generate Alphabetic Sequence with Current Year In SQL

问题

How can we write a SQL function which can generate 'Sequence_Code' like AA,AB,AC....AZ. BA,BB,BC.... with the combination of last two digit of 'Current_Year' for each 'ID'. Order by 'Record_Date'

For instance: If Current_Year of First row is is 2019, then Sequence_Code should be 19AA. My table is LoadData

Sequence_Code	ID	Current_Year	Record_Date
NULL	310001	2019	2019-01-01
NULL	310002	2018	2018-02-22
NULL	310003	2020	2020-02-20
NULL	310004	2020	2020-02-10

Expected Output is:

Sequence_Code	ID	Current_Year	Record_Date
19AA	310001	2019	2019-01-01
18AB	310002	2018	2018-02-22
20AC	310003	2020	2020-02-20
20AD	310004	2020	2020-02-10

回答1:

With ROW_NUMBER() window function and math:

WITH cte AS (SELECT *, ROW_NUMBER() OVER (ORDER BY Record_Date) rn FROM LoadData)
SELECT RIGHT(Current_Year, 2) + 
       CHAR(ASCII('A') + rn / 26 + CASE rn % 26 WHEN 0 THEN -1 ELSE 0 END) + 
       CHAR(ASCII('A') - 1 + CASE rn % 26 WHEN 0 THEN 26 ELSE rn % 26 END) Sequence_Code,
       ID, Current_Year, Record_Date
FROM cte
ORDER BY rn

If you want to update the column Sequence_Code of the table:

WITH cte AS (SELECT *, ROW_NUMBER() OVER (ORDER BY Record_Date) rn FROM LoadData)
UPDATE cte
SET Sequence_Code = RIGHT(Current_Year, 2) + 
                    CHAR(ASCII('A') + rn / 26 + CASE rn % 26 WHEN 0 THEN -1 ELSE 0 END) + 
                    CHAR(ASCII('A') - 1 + CASE rn % 26 WHEN 0 THEN 26 ELSE rn % 26 END)

See the demo.
Results:

> Sequence_Code |     ID | Current_Year | Record_Date
> :------------ | -----: | -----------: | :----------
> 18AA          | 310001 |         2018 | 2018-01-01 
> 19AB          | 310002 |         2019 | 2019-02-22 
> 20AC          | 310004 |         2020 | 2020-02-10 
> 20AD          | 310003 |         2020 | 2020-02-20

回答2:

The simplest method might be to generate all combinations and enumerate them:

with alpha as (
      select 'A' as alpha union all
      select 'B' as alpha union all
      . . .  -- continue for the rest of the letters
      select 'Z' as alpha
     ),
     alphas as (
      select concat(a1.alpha, a2.alpha) as alpha2,
             row_number() over (order by a1.alpha, a2.alpha) as seqnum
      from alpha a1 cross join
           alpha a2
     )
select current_year || alpha2.alpha2 as sequence_code, t.*
from (select t.*,
             row_number() over (partition by current_year order by record_date) as seqnum
      from LoadData t
     ) t left join
     alpha2 
     on t.seqnum = a2.seqnum;

Note: This uses standard SQL, so the functionality may have different syntax depending on the database.

来源：https://stackoverflow.com/questions/65494479/is-there-any-way-to-generate-alphabetic-sequence-with-current-year-in-sql

标签

sql

sql-server

tsql

sql-server-2017