SQL-Anzahl leere Zellen in unbekannter Anzahl von Spalten

Question

Ich habe eine Tabelle mit einer unbekannten Anzahl von Spalten (und auch unbekannte Spaltennamen) mit verschiedenen Arten von Daten (kann alles von Bit bis Nvarchar oder Datetime) wie folgt sein:

ID | Col2 | Col3 | Customer | ..(etc).. 
1 | NULL | 0 | CustA |  
2 | valA | 1 | NULL | 
3 | valB | NULL | (empty) | 

ich brauche eine Abfrage, die alle NULL und leere Zellen auf jeder Spalte zählt und gibt das Ergebnis wie folgt aus:

Column_Name | No_Of_Empty_And_Null_Cells | 
    Col2  |    1    | 
    Col3  |    1    | 
Customer |    2    | 
(etc...) |        | 

ich verstehe, dass ich dynamische Abfragen und UNPIVOT, aber meine SQL-Kenntnisse verwenden ist nicht annähernd das!

How to count all NULL values in a table? scheint nicht, wie es ist MySQL Zusammenhang mit der Arbeit, nicht MS SQL

Answer 1

Sie können diese dynamischen SQL-Code ausprobieren:

DECLARE @schema VARCHAR(100)='dbo'; 
DECLARE @tableName VARCHAR(100)='SomeTable'; 

DECLARE @DynamicSelect VARCHAR(MAX)= 
(
    STUFF((SELECT 'UNION SELECT ''' + COLUMN_NAME + ''' AS COLUMN_NAME' + 
     ', (SELECT COUNT(*) FROM ' + @schema + '.' + @tableName + ' WHERE [' + COLUMN_NAME + '] IS NULL) AS No_Of_Null_Cells ' 
     FROM INFORMATION_SCHEMA.COLUMNS AS c 
     WHERE c.TABLE_SCHEMA=@schema AND c.TABLE_NAME=@tableName AND c.IS_NULLABLE='YES' 
     FOR XML PATH('') 
     ),1,6,'') 
); 
exec (@DynamicSelect) 


DECLARE @DynamicSelect2 VARCHAR(MAX)= 
(
    STUFF((SELECT 'UNION SELECT ''' + COLUMN_NAME + ''' AS COLUMN_NAME' + 
     ', (SELECT COUNT(*) FROM ' + @schema + '.' + @tableName + ' WHERE LTRIM(RTRIM([' + COLUMN_NAME + '])) ='''') AS No_Of_Empty_Cells ' 
     FROM INFORMATION_SCHEMA.COLUMNS AS c 
     WHERE c.TABLE_SCHEMA=@schema AND c.TABLE_NAME=@tableName AND c.DATA_TYPE LIKE '%char%' 
     FOR XML PATH('') 
     ),1,6,'') 
); 
exec (@DynamicSelect2) 

Answer 2

EDIT: Diese Antwort für MySQL ist (nicht sorgfältig zuerst gelesen hat)

Von this answer

, ich denke, das Ergebnis wird Ihr alle "null" Zellen zählen:

SET @db = 'your_database_name'; -- database 
SET @tb = 'your_table_name'; -- table 
SET @x = ''; -- will hold the column names with ASCII method applied to retrieve the number of the first char 
SET @numcolumns = 0; -- will hold the number of columns in the table 

-- figure out how many columns we have 
SELECT count(*) into @numcolumns FROM information_schema.columns where table_name=@tb and table_schema=@db; 

-- we have to prepare some query from all columns of the table 
SELECT group_concat(CONCAT('ASCII(',column_name,')')) into @x from information_schema.columns where table_name=@tb and table_schema=@db; 
-- after this query we have a variable separated with comma like 
-- ASCII(col1),ASCII(col2),ASCII(col3) 

-- we now generate a query to concat the columns using comma as separator (null values are omitted from concat) 
-- then figgure out how many times the comma is in that substring (this is done by using length(value)-length(replace(value,',','')) 
-- the number returned is how many non null columns we have in that column 
-- then we deduct the number from the known number of columns, calculated previously 
-- the +1 is added because there is no comma for single value 
SET @s = CONCAT('SELECT @numcolumns - (length(CONCAT_WS(\',\',', @x, '))-length(replace(CONCAT_WS(\',\',', @x, '),\',\',\'\')) + 1) FROM ',@db,'.',@tb,';'); 
PREPARE stmt FROM @s; 
EXECUTE stmt; 
-- after this execution we have returned for each row the number of null columns 
-- I will leave to you to add a sum() group call if you want to find the null values for the whole table 
DEALLOCATE PREPARE stmt; 

Answer 3

Hier ist eine Methode zum Zurückgeben der Felder mit Null oder leere Werte aus einer Tabelle.
Über das Generieren und Ausführen einer dynamischen Abfrage mit einem Unpivot.
auf einem SQL Server getestet 2014.

DECLARE @SchemaName SYSNAME = 'YourDatabase'; 
DECLARE @TableName SYSNAME = 'YourTable'; 

DECLARE @SQL NVARCHAR(MAX); 

WITH COL AS (
    SELECT c.name 
    FROM sys.objects o 
    INNER JOIN sys.schemas s ON o.[schema_id] = s.[schema_id] 
    INNER JOIN sys.columns c ON o.[object_id] = c.[object_id] 
    WHERE o.[type] = 'U' 
     AND s.name = @SchemaName 
     AND o.name = @TableName 
     AND c.is_nullable = 1 
) 
SELECT @SQL = 'SELECT up.column_name, up.total_empty 
FROM (
SELECT ' + CHAR(13) + STUFF((
    SELECT CHAR(13) + ', ' + QUOTENAME(name) + ' = SUM(IIF(LEN(RTRIM(' + QUOTENAME(name) + '))>0,0,1))' 
    FROM COL 
    FOR XML PATH(''), TYPE).value('.', 'VARCHAR(MAX)'), 1, 2, ' ') + ' 
FROM ' + QUOTENAME(@SchemaName) + '.' + QUOTENAME(@TableName) + ') q 
UNPIVOT 
(total_empty for column_name in ('+ 
    STUFF((
    SELECT CHAR(13) + ', ' + QUOTENAME(name) FROM COL 
    FOR XML PATH(''), TYPE).value('.', 'VARCHAR(MAX)'), 1, 2, ' ') 
    +') 
) up where up.total_empty > 0 order by up.column_name'; 

--SELECT @SQL; 
EXEC sys.sp_executesql @SQL;