将查询从 PLSQL 迁移到 SQL 服务器

Question

我这部分代码是用PL/SQL

写的

 if l_rec.sched_interval_type = 'DAYS' then    

      if l_max_date is null then     

        if l_rec.DAY_START_DAY is not null then     
           SELECT next_day(p_date, l_rec.DAY_START_DAY)    
           INTO l_start_date    
           FROM dual;    
        else    
           l_start_date := TRUNC(p_date);    
        end if;    

      else -- previous schedule recs exist...    

         if l_rec.DAY_START_DAY is not null then     
           SELECT next_day(GREATEST(l_max_date, p_date), l_rec.DAY_START_DAY)    
           INTO l_start_date    
           FROM dual;    
         else    
           l_start_date := l_max_date + l_rec.SCHED_AVAIL_DAYS;    
         end if;    

      end if;

我需要把它转换成SQL服务器

select 
CASE WHEN @l_max_date is null then    

    SELECT @l_start_date = CASE WHEN (SELECT sched_interval_type from #l_rec)  = 'DAYS' and @l_max_date is null and  @NextDayID is not null then    
    DATEADD(DAY, (DATEDIFF(DAY, ((@NextDayID + 5) % 7),@p_date) / 7) * 7 + 7, ((@NextDayID + 5) % 7))
          else CONVERT(DATETIME, CONVERT(DATE, @p_date)) end 
          from #l_rec

     ELSE -- previous schedule recs exist...    

  SELECT @l_start_date = CASE WHEN (SELECT sched_interval_type from #l_rec)  = 'DAYS' and @l_max_date is null and  @NextDayID is not null then    
          DATEADD(DAY, (DATEDIFF(DAY, ((@NextDayID + 5) % 7), [dbo].[greatest](@l_max_date, @p_date)) / 7) * 7 + 7, ((@NextDayID + 5) % 7))
              else @l_max_date+ (SELECT SCHED_AVAIL_DAYS from #l_rec) end 
              from #l_rec
         END

我对 case.. when 有疑问。有办法修改吗？

Answer 1

在 TSQL 中，CASE表达式returns某种类型的单个值。（没有 CASE 语句。）您可以使用类似的东西：

set @L_Start_Date = case
  when @L_Max_Date is null then
    ( select ... )
  when <some other condition> then
    ( some other expression that results in a single value )
  else
    ( expression that provides a default value )
  end

请注意，在 SELECT 中不执行向变量赋值，它只是 returns 向 CASE 赋值。

Answer 2

试试这个...

SELECT @l_start_date = 
        CASE 
            WHEN @l_max_date is null THEN
                CASE 
                    WHEN sched_interval_type = 'DAYS' AND @l_max_date IS NULL AND @NextDayID IS NOT NULL THEN DATEADD(DAY, (DATEDIFF(DAY, ((@NextDayID + 5) % 7),@p_date) / 7) * 7 + 7, ((@NextDayID + 5) % 7))
                    ELSE CONVERT(DATETIME, CONVERT(DATE, @p_date)) 
                END
            ELSE
                CASE 
                    WHEN sched_interval_type = 'DAYS' AND @l_max_date IS NULL AND @NextDayID IS NOT NULL THEN DATEADD(DAY, (DATEDIFF(DAY, ((@NextDayID + 5) % 7), [dbo].[greatest](@l_max_date, @p_date)) / 7) * 7 + 7, ((@NextDayID + 5) % 7))
                    ELSE @l_max_date+ SCHED_AVAIL_DAYS
                END
         END 
FROM #l_rec

将查询从 PLSQL 迁移到 SQL 服务器

Migrate a query from PLSQL TO SQL SERVER

tsql

sql-server

plsql