Find All Rows With Null Value(s) in Any Column

问题:

I'm trying to create a query that will return all the rows that have a null value across all but 1 column. Some rows will have more than one null entry somewhere. There is one column I will want to exclude, because at this moment in time all of the entries are null and it is the only column that is allowed to have null values. I am stuck because I don't know how to include all of the columns in the WHERE.

SELECT *
FROM Analytics
WHERE * IS NULL

Alternatively, I can do a count for one column, but the table has about 67 columns.

SELECT COUNT(*)
FROM Analytics
WHERE P_Id IS NULL

回答1:

In SQL Server you can borrow the idea from this answer

;WITH XMLNAMESPACES('http://www.w3.org/2001/XMLSchema-instance' as ns)
SELECT *
FROM   Analytics
WHERE  (SELECT Analytics.*
        FOR xml path('row'), elements xsinil, type
        ).value('count(//*[local-name() != "colToIgnore"]/@ns:nil)', 'int') > 0

SQL Fiddle

Likely constructing a query with 67 columns will be more efficient but it saves some typing or need for dynamic SQL to generate it.

回答2:

I don't have such a table to test, assuming there is no 'x' as data in any field, I think this should work on Sql-Server; (DEMO)

NOTE: I have filtered keyColumn as c.name != 'keyColumn'

DECLARE @S NVARCHAR(max), @Columns VARCHAR(50), @Table VARCHAR(50)

SELECT @Columns = '66', --Number of cols without keyColumn
       @Table = 'myTable'

SELECT @S =  ISNULL(@S+'+ ','') + 'isnull(convert(nvarchar, ' + c.name + '),''x'')'  
FROM sys.all_columns c 
WHERE c.object_id = OBJECT_ID(@Table) AND c.name != 'keyColumn'

exec('select * from '+@Table+' where ' + @S + '= replicate(''x'',' + @Columns + ')')

回答3:

Depending on which RDBMS you're using, I think your only option (rather than explicitly saying WHERE col1 IS NULL and col2 IS NULL and col3 IS NULL ...) would be to use Dynamic SQL.

For example, if you want to get all the column names from a SQL Server database, you could use something like this to return those names:

SELECT
     name
FROM
     sys.columns
WHERE
     object_id = OBJECT_ID('DB.Schema.Table')

You could use FOR XML to create your WHERE clause:

SELECT Name + ' IS NULL AND ' AS [text()]
FROM sys.columns c1
WHERE     object_id = OBJECT_ID('DB.Schema.Table')
ORDER BY Name
FOR XML PATH('')

Hope this helps get you started.

Good luck.