Question

我想多次选择一些行，具体取决于列的值。

来源表

Article | Count
===============
A       | 1
B       | 4
C       | 2

通缉结果

Article
===============
A
B
B
B
B
C
C

请提供任何提示或样品？

Answer 1

您可以使用：

SELECT m.Article
FROM mytable m
CROSS APPLY (VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10)) AS s(n)
WHERE s.n <= m.[Count];

的 LiveDemo

注意：CROSS APLLY包含任何计数表。这里的值最多为10。

相关：What is the best way to create and populate a numbers table?

Answer 2

您还可以使用递归CTE，它与数字＆gt;一起使用。 10（这里最多1000）：

With NumberSequence( Number ) as
(
    Select 0 as Number
        union all
    Select Number + 1
        from NumberSequence
    where Number BETWEEN 0 AND 1000
)
SELECT Article
FROM ArticleCounts
CROSS APPLY NumberSequence
WHERE Number BETWEEN 1 AND [Count] 
ORDER BY Article
Option (MaxRecursion 0)

Demo

数字表肯定是最好的选择。

http://sqlperformance.com/2013/01/t-sql-queries/generate-a-set-2

Answer 3

请检查以下SQL脚本在执行SELECT语句之前，请注意我使用了一个用于模拟数字表的用户函数您可以在参考教程

中找到numbers table in SQL Server的sql代码

----create table myTempTbl (Article varchar(10), Count int)
--insert into myTempTbl select 'A',1
--insert into myTempTbl select 'B',4
--insert into myTempTbl select 'C',2

select t.* 
from myTempTbl t
cross apply dbo.NumbersTable(1,100,1) n
where n.i <= t.Count
order by t.Article

Answer 4

再多一次CTE

with cte_t as (
    select c as c, 1 as i
        from mytable
        group by c
    union all
    select t.c, ctet.i + 1
        from mytable t
            join cte_t ctet
                on ctet.c = t.c  
                    and ctet.i < t.i
)
select cte_t.c
    from cte_t
    order by cte_t.c

Answer 5

可以使用简单的 WHILE LOOP

获取输出

      DECLARE @table TABLE 
        (ID int ,Article varchar(5),[Count] int)

        INSERT INTO @table
        (ID,Article,Count)
        VALUES
        (1,'A',1),(2,'B',4),(3,'C',2)

        DECLARE @temp TABLE 
        (Article varchar(5))

        DECLARE @Cnt1 INT
        DECLARE @Cnt2 INT
        DECLARE @Check INT
        DECLARE @max INT
        SET @max =0
        SET @Cnt1 = (SELECT Count(Article) FROM @table)

        WHILE (@max < @Cnt1)
        BEGIN
            SET @max = @max +1
            SET @Cnt2 =  (SELECT  [Count] FROM @table WHERE ID =@max)
            SET @Check =(SELECT [Count] FROM @table WHERE ID =@max)
            WHILE (@Cnt2 > 0)
            BEGIN
                INSERT INTO @temp
                SELECT Article FROM @table WHERE [Count] =@Check
                SET @Cnt2 = @Cnt2 -1
            END   
        END
        SELECT * FROM @temp

SQL在SELECT中乘以行

5 个答案: