SQL 中的单个条件 select 查询

Question

我有以下 table 文件名。

filename   flag
fileA       1
fileB       0
fileC       0
fileD       1
fileA       1

我想要这个 table 中所有不同的文件名并且如果任何文件名的标志为 1，我希望将该文件名替换为 4 个文件名，如 FilaA_part_1、FilaA_part_2、FilaA_part_3、FilaA_part_4.

输出应该是

FilaA_part_1
FilaA_part_2
FilaA_part_3
FilaA_part_4
fileB      
fileC
FilaD_part_1
FilaD_part_2
FilaD_part_3
FilaD_part_4

我可以通过临时 table 实现这一点。我想知道是否可以使用单个 select 查询。

我能到达

SELECT DISTINCT CASE WHEN FLAG=1 THEN FILENAME + '_part_1' 
ELSE FILENAME END
FROM FILENAMES

Answer 1

工会应该做的：

SELECT FILENAME
FROM FILENAMES
WHERE FLAG = 0
UNION 
SELECT FILENAME + '_part_1'
FROM FILENAMES
WHERE FLAG = 1
UNION 
SELECT FILENAME + '_part_2'
FROM FILENAMES
WHERE FLAG = 1
UNION 
SELECT FILENAME + '_part_3'
FROM FILENAMES
WHERE FLAG = 1
UNION 
SELECT FILENAME + '_part_4'
FROM FILENAMES
WHERE FLAG = 1

Answer 2

试试这个应该在 sql 服务器 2000

中工作

SELECT filename + '_part' + num
FROM   Yourtable
       CROSS JOIN (SELECT '_1' num
                   UNION ALL
                   SELECT '_2'
                   UNION ALL
                   SELECT '_3'
                   UNION ALL
                   SELECT '_4') A
WHERE  flag = 1
UNION ALL
SELECT filename
FROM   Yourtable B
WHERE  NOT EXISTS (SELECT 1
                   FROM   Yourtable A
                   WHERE  a.filename = b.filename
                          AND a.flag = 1)

SQLFIDDLE DEMO

Answer 3

declare @i varchar(10) 
set @i =1 
create table #temp ([filename] varchar(50)) 
while (@i <= 4) 
begin 
    insert into #temp([filename]) 
    SELECT distinct 
           case when flag = 1 then [filename]+'Part_'+@i 
                              else [filename] 
           end [filename] 
    FROM ( 
        SELECT 'fileA'[filename] ,1 flag 
        UNION ALL 
        SELECT 'fileB',0 
        UNION ALL 
        SELECT 'fileC', 0 
        UNION ALL 
        SELECT 'fileD', 1 
        UNION ALL 
        SELECT 'fileA' , 0 
    ) BASE 
    set @i= @i+1 
end 
select distinct [filename] from #temp

Answer 4

试试这个查询。

SELECT filename + '_part' + num
FROM   FILENAMES
   CROSS JOIN (SELECT '_1' num
               UNION ALL
               SELECT '_2'
               UNION ALL
               SELECT '_3'
               UNION ALL
               SELECT '_4') A
WHERE  flag = 1
UNION ALL
SELECT filename
FROM   FILENAMES B
WHERE  NOT EXISTS (SELECT 1
               FROM   FILENAMES A
               WHERE  a.filename = b.filename
                      AND a.flag = 1)

Answer 5

这是您在 Q 中 post 的准确输出，我希望这对您有所帮助

declare @temp table
(filenames nvarchar(44),   flag int
)
insert into @temp values ('fileA',      1)
insert into @temp values ('fileB',      0)
insert into @temp values ('fileC',      0)
insert into @temp values ('fileD',      1)
insert into @temp values ('fileA',      0);

; with cte as(
select filenames,flag from @temp t1 where not exists (select 1 from @temp t2 where t1.filenames = t2.filenames AND t2.flag = 1)
union 
select filenames + '_part_1',flag from @temp where flag = 1
union                       
select filenames + '_part_2',flag from @temp where flag = 1
union                       
select filenames + '_part_3',flag from @temp where flag = 1
union                       
select filenames + '_part_4',flag from @temp where flag = 1)

select * FROM cte

SQL 中的单个条件 select 查询

Single conditional select query in SQL

sql

sql-server

sql-server-2000