在 Select query 中合并三个表，每个表中的规则 3、2、1 记录

Question

在 Select 查询中按规则 3、2、1 合并每个表中的三个表，如下所示：

• 表A：ID、字段A、字段B、字段C、....
• 表 B：ID、字段A、字段B、字段C、....

• TableC：ID、FieldA、FieldB、FieldC、....

• ID：每张表自动编号

• FieldA 在所有三个表中都是唯一的。

我正在寻找一个Select 查询来合并三个表，如下所示：

• 来自TableA的前三条记录按ID排序
• TableB 的前两条记录按 ID 排序
• 来自TableC的前1条记录，按ID排序

重复此操作，直到从所有三个表中选择所有记录。

如果某些表的记录较少或不符合条件，请忽略该表并继续其他表。

我的尝试：

我完全是通过编程方式完成的，比如 SQL Server 存储过程中的游标和If 条件。

这会造成延迟。

Answer 1

这需要一个公式，该公式从每个表中获取行号并将其转换为一系列跳过所需值的整数。

在下面的查询中，为了缩短公式，我添加了一些 CTE。真正的魔力在于UNION。另外，我正在为您的控件添加一个附加字段。随意摆脱它。

WITH A_Aux as (
SELECT 'A' As FromTable, ROW_NUMBER() OVER (ORDER BY ID) AS RowNum, TableA.*
FROM TableA
), B_Aux AS (
SELECT 'B' As FromTable, ROW_NUMBER() OVER (ORDER BY ID) AS RowNum, TableB.*
FROM TableB
), C_Aux AS (
SELECT 'C' As FromTable, ROW_NUMBER() OVER (Order BY ID) AS RowNum, TableC.*
FROM TableC
)
SELECT *
FROM (
    SELECT RowNum+3*FLOOR((RowNum-1)/3) As ColumnForOrder, A_Aux.* FROM A_Aux
    UNION ALL
    SELECT 3+RowNum+4*FLOOR((RowNum-1)/2), B_Aux.* FROM B_Aux
    UNION ALL
    SELECT 6*RowNum, C_Aux.* FROM C_Aux
) T
ORDER BY ColumnForOrder

PS：注意Offset + RowNum + (6-N) * Floor((RowNum-1)/N) 将 N 条记录组合在一起的模式（对于TableC，它当然简化了很多）。

PPS：我手头没有 SQL 服务器来测试它。如果有语法错误，请告诉我。

Answer 2

你可以试试这个..

    GO

    select * into #temp1 from (select  * from  table1) as t1
    select * into #temp2 from (select  * from  table2) as t2
    select * into #temp3 from (select  * from  table3) as t3

    select * into #final from (select col1, col2, col3 from #temp1 where 1=0) as tb

    declare @i int

    set @i=1
    while( (select COUNT(*) from #temp1)>@i)
    Begin

    ;with ct1 as (
    select ROW_NUMBER() over (order by id) as Slno, * from #temp1
    ),ct2 as (
    select ROW_NUMBER() over (order by id) as Slno, * from #temp2
    ),ct3 as (
    select ROW_NUMBER() over (order by id) as Slno, * from #temp3
    ),cfinal as (
    select top 3 * from #temp1
    union all
    select top 2 * from #temp2
    union  all
    select top 1 * from #temp3
    )
    insert into #final ( col1 , col2, col3 )
    select col1, col2, col3 from cfinal

    delete from #temp1 where id in (select top 3 ID from #temp1)
    delete from #temp2 where id in (select top 2 ID from #temp2)
    delete from #temp3 where id in (select top 1 ID from #temp3)

    set @i = @i+1

    End

    Select * from #final

    Drop table #temp1
    Drop table #temp2
    Drop table #temp3

    GO

首先为所有 3 个表创建临时表，每次插入删除插入的记录，如果我这边没有任何遗漏，这将为您带来所需的结果。 如果可行，请注意这一点。

Answer 3

这里没有太多信息可以参考，但我假设您可以使用 UNION 来组合多个语句。

SELECT * TableA ORDER BY ID DESC OFFSET 3 ROWS 
UNION
SELECT * TableB ORDER BY ID DESC OFFSET 2 ROWS 
UNION
SELECT * TableC ORDER BY ID DESC OFFSET 1 ROWS 

执行并查看是否有效。

/AF

Answer 4

据我了解，我创建了三个临时表，分别为 ta、tb、tc。

select * into #ta from (
select 'A' a
union all
select 'A' a
union all
select 'A' a
union all
select 'A' a
union all
select 'A' a
union all
select 'A' a
union all
select 'A' a
) a

select * into #tb from (
select 'B' b
union all
select 'B' 
union all
select 'B' 
union all
select 'B' 
union all
select 'B' 
) b

select * into #tc from (
select 'C' c
union all
select 'C' 
union all
select 'C' 
union all
select 'C' 
union all
select 'C' 
) c

如果表与您的表匹配，则输出类似于 A,A,A,B,B,C,A,A,A,B,B,C,A,B,C,C,C

T-SQL

declare @TAC int = (select count (*) from #ta)      -- Table A Count = 7
declare @TBC int = (select count (*) from #tb)      -- Table B Count = 5

declare @TAR int = @TAC % 3                         -- Table A Reminder = 1  
declare @TBR int = @TBC % 2                         -- Table B Reminder = 1 

declare @TAQ int = (@TAC - @TAR) / 3                -- Table A Quotient = (7 - 1) / 3 = 2, is will passed on NTILE
                                                    -- So we gonna split as two group (111), (222)
declare @TBQ int = (@TBC - @TBR) / 2                -- Table B Quotient = (5 - 1) / 2 = 2, is will passed on NTILE
                                                    -- So we gonna split as two group (11), (22)

select * from (
 select *, NTILE (@TAQ) over ( order by a) FirstOrder, 1 SecondOrder from (
  select top (@TAC - @TAR) * from #ta order by a
 ) ta                                               -- 6 rows are obtained out of 7.
 union all 
 select *, @TAQ + 1, 1 from (
  select top (@TAR) * from #ta order by a desc
 ) ta                                               -- Remaining one row is obtained. Order by desc is must
                                                    -- Here FirstOrder is next value of previous value. 
 union all

 select *, NTILE (@TBQ) over ( order by b), 2  from (
  select top (@TBC - @TBR) * from #tb order by b
 ) tb                                               
 union all 
 select *, @TBQ + 1, 2 from (
  select top (@TBR) * from #tb order by b desc
 ) tb           

 union all 

 select *, ROW_NUMBER () over (order by c), 3 from #tc                                  
) abc order by FirstOrder, SecondOrder  

让我解释一下 T-SQL： 在此之前，FYR：NTILE 和 Row Number

1. 获取计数。
2. 找到将传递给 NTILE 函数的商。
3. 按 NTILE 值和静态排序。

注意：

1. 我使用的是 SQL Server 2017。
2. 如果 T-SQL 工作正常，那么您需要更改 order by <yourcolumn> 中的列。