我该如何解决这个问题？

Question

我有一个表格，包括1列ID和12个月的月份（Month01到Month12）。如果我有一个参数@月= 9，我怎么可以比较获得列Month01到Month09没有Month10，Month11，Month12。请帮帮我！

Answer 1

，你也可以尝试了这一点:)

DECLARE @month int = 9 
DECLARE @Sql nvarchar(100) ='' 
DECLARE @pos int = 1 
WHILE(@pos <= @month) 
BEGIN 
    SET @Sql = @Sql + (',month' + right('00'+ rtrim(@pos), 2)) 
    SET @pos = @pos + 1 
END 
SET @Sql= 'SELECT ID ' +@Sql + ' FROM table' 
EXEC sp_executesql @Sql 

Answer 2

DECLARE @month int 
DECLARE @tableName nvarchar(128) 

SET @month = 9; 
SET @tableName = 'months' -- YOUR TABLE's NAME 

DECLARE @query nvarchar(2048) 
SET @query = 
'SELECT id, ' + STUFF((SELECT DISTINCT ', ' + name 
    FROM sys.columns WHERE name LIKE'Month%' 
    AND object_id = OBJECT_ID(@tableName) 
    AND CONVERT(INT, RIGHT(name, 2)) <= @month 
    FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'),1,1,'') 
    + ' FROM ' + @tableName; 

EXEC(@query) 

Answer 3

厮磨的回答是更优雅，但下面是一个另类的“基本”的方式来做到这一点：

DECLARE @month INT 
SET @month = 9 

IF @Month = 1 
BEGIN 
    SELECT Id, Month01 
    FROM MonthlyData 
END 

IF @Month = 2 
BEGIN 
    SELECT Id, Month01, Month02 
    FROM MonthlyData 
END 

-- Repeat for months 3-9 

IF @Month = 9 
BEGIN 
    SELECT Id, Month01, Month02, Month03, Month04, 
     Month05, Month06, Month07, Month08, Month09 
    FROM MonthlyData 
END 

-- Repeat for months 10-12 

见我SQL Fiddle。

Answer 4

declare @str varchar(1000) 

SELECT @str= coalesce(@str + ', ', '') + a.name 
FROM (
     Select name from sys.columns 
     where object_id = OBJECT_ID('table_months') 
     and isnumeric(right(name,2))= 1 and name like 'month%' 
     and cast(right(name,2) as int) < '03') a 

- 而不是 '03' 的你使用一个变量并分配所需的飞蛾数量

declare @sql nvarchar(100) 

set @sql = 'select ID, '+ @str+' from table_months' 

exec sp_executesql @sql