需要优化SQL Server查询

Question

I have a table with 'n' columns & I have to write a simple query this way :

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

Please suggest me better logic for the same.

Can there be something like :

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.

This is specific to MS SQL Server 2005 only.

Answer 1

if there are a lot of columns or the number of columns is unknown you could use dynamic sql to get the job done, probably not the best way though:

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

The only way I can see you can write a little less code (which have nothing to do with optimization) is not to check non-null columns.
If it's a puzzle or a test question, you might probably use the fact that anything+null = null (please, don't do it in real application), so it will look

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)