Question

我有一个带'n'列的表＆安培;我必须用这种方式编写一个简单的查询：

SELECT col_1,col_2,col_3,...col_n FROM SingleTableOnly 
WHERE col_1 IS NOT NULL
AND col_2 IS NOT NULL
AND col_3 IS NOT NULL
... -- for each column i need to put this condition again & again
AND col_n IS NOT NULL

请建议我更好的逻辑。

可以有类似的东西：

SELECT ALL COLUMNS FROM SingleTableOnly 
WHERE ALL COLUMNS IS NOT NULL
-- i know this isnt right sql query, but trying to figure something where i can write less.

这仅适用于MS SQL Server 2005。

Answer 1

如果有很多列或列数未知，您可以使用动态SQL来完成工作，但可能不是最好的方法：

declare @sql varchar(4000)
set @sql = ' where 1=1 '
declare my_cursor cursor
for

SELECT
    COLUMN_NAME
FROM   
  INFORMATION_SCHEMA.COLUMNS 
WHERE   
  TABLE_NAME = 'tablename' 
ORDER BY 
  ORDINAL_POSITION ASC; 

open my_cursor
declare @colname varchar(20)
fetch next from my_cursor into @colname
while(@@FETCH_STATUS <> -1)
begin
set @sql = @sql + ' and ' + @colname + ' is not null '

fetch next from my_cursor into @colname
end

close my_cursor
deallocate my_cursor

--select 'select * from tablename ' +  @sql
EXEC('select * from tablename ' +  @sql)

Answer 2

DECLARE @TableName VARCHAR(100)
SET @TableName = 'Your_Table_Name'

DECLARE @columns VARCHAR(MAX)

SELECT @columns = STUFF((SELECT ' and '+COLUMN_NAME +' IS NOT NULL ' FROM  INFORMATION_SCHEMA.COLUMNS WHERE   TABLE_NAME = @TableName  ORDER BY ORDINAL_POSITION ASC FOR XML PATH('')),1,4,'')

EXEC('SELECT * FROM ' + @TableName ' WHERE ' + @sql)

Answer 3

我能看到的唯一方法是编写少量代码（与优化无关），不检查非空列。
如果它是一个谜题或一个测试问题，你可能会使用任何事实+ null = null（请不要在实际应用中这样做），所以它会看起来

WHERE ((int_field1+int_field2+ intfield_n) IS NOT NULL)  
AND ((string_field1+string_field2+...) IS NOT NULL)
AND ((datetime_field1+datetime_field2+...) IS NOT NULL)

需要优化sql server查询

3 个答案: