有什么方法可以生成当前年份的字母序列 SQL

Question

我们如何编写一个 SQL 函数来生成 'Sequence_Code' 像 AA,AB,AC....AZ。 BA,BB,BC....每个 'ID' 的最后两位数 'Current_Year' 的组合。按 'Record_Date'

排序

例如：如果第一行的Current_Year是2019，那么Sequence_Code应该是19AA。我的 table 是 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

预期输出为：

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

Answer 1

最简单的方法可能是生成所有组合并枚举它们：

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;

注意：这使用标准 SQL，因此功能可能具有不同的语法，具体取决于数据库。

Answer 2

使用 ROW_NUMBER() window 函数和数学：

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

如果要更新 table 的第 Sequence_Code 列：

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)

参见demo。
结果：

> 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

有什么方法可以生成当前年份的字母序列 SQL

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

sql

tsql

sql-server

sql-server-2017