asked on

Single row for Count(column is NULL), Count(all rows)

Hi all

Does anyone have some quick and dirty (copyright jimpen) T-SQL to return a set with a single row that contains a count of all rows where a specific value is NULL (say column_name), and a count of the rows in the entire table (say table_name)?

I've put together the below CTE, which works fine, but it seems like there's a more elegant way to do this that I'm not grasping.

Thanks in advance.
Jim

;
WITH m as (
	SELECT 'Account' as label, COUNT(id) as row_count_column_name_missing
	FROM table_name
	WHERE column_name IS NULL)
, a as (	
	SELECT 'Account' as label, COUNT(id) as row_count_all
	FROM table_name) 
SELECT 
	m.label, 
	m.row_count_column_name_missing, 
	a.row_count_all,
	CAST(m.row_count_column_name_missing / CAST(row_count_all as numeric(19,4)) * 100 as numeric(5,2)) as pct_missing
FROM m
	JOIN a ON m.label = a.label

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Ray

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Scott Pletcher

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Ray

Too many irons in the fire this morning, Thanks for tidying it up Scott! :-)

Jim Horn

ASKER

Simpler yes, but on a table with 1m rows this takes 7 seconds vs. 1 second for the CTE approach.

Tinkering, tinkering..

Ray

Sorry JIm, I wasn't 'reading into' the question.

awking00

select 'account' as label, count(*) as row_count_all, count(column_name) as row_count_column_name_missing,
cast((count(column_name)/count(*)) * 100 as numeric(5,2)) as pct_missing
from yourtable;

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Scott Pletcher

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SOLUTION

Vitor Montalvão

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awking00

Actually, I guess row_count_column_name_missing should be count(*) - count(column_name).

Jim Horn

ASKER

Cleared the cache, set statistics io and time on, and reran both my proposed and the new code here.
New code is half the elapsed time and simpler, so I'll go with that.

Code #1 - My original

DBCC FREEPROCCACHE
SET STATISTICS IO ON
SET STATISTICS TIME ON                     
;
WITH m as (
	SELECT 'Account' as label, COUNT(id) as row_count_column_name_missing
	FROM SF_Account_1
	WHERE Address1_BioIQ__c IS NULL)
, a as (	
	SELECT 'Account' as label, COUNT(id) as row_count_all
	FROM SF_Account_1) 
SELECT 
	m.label, 
	m.row_count_column_name_missing, 
	a.row_count_all,
	-- CAST(m.row_count_column_name_missing / CAST(row_count_all as numeric(19,4))) * 100 as numeric(5,2)) as pct_missing
	100 - CAST(m.row_count_column_name_missing / CAST(row_count_all as numeric(19,4)) * 100 as numeric(5,2))
FROM m
	JOIN a ON m.label = a.label

SET STATISTICS IO OFF
SET STATISTICS TIME OFF

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Results #1

DBCC execution completed. If DBCC printed error messages, contact your system administrator.

(1 row(s) affected)
Table 'SF_Account_1'. Scan count 34, logical reads 636238, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

 SQL Server Execution Times:
   CPU time = 2651 ms,  elapsed time = 577 ms.

 SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 0 ms.

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Code #2 - Proposed here, with minor modificaitons

DBCC FREEPROCCACHE
SET STATISTICS IO ON
SET STATISTICS TIME ON  
 
SELECT 
	a.col_name_null_count, 
	a.total_rows_in_table, 
	a.col_name_null_count / CAST(a.total_rows_in_table as numeric(19,4)) as pct_missing
FROM (
	select 
		SUM(CASE WHEN Address1_BioIQ__c IS NULL then 1 else 0 end ) AS col_name_null_count,  
		COUNT(*) as total_rows_in_table
	FROM SF_Account_1) a
                           
SET STATISTICS IO OFF
SET STATISTICS TIME OFF

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Results #2

DBCC execution completed. If DBCC printed error messages, contact your system administrator.

(1 row(s) affected)
Table 'SF_Account_1'. Scan count 17, logical reads 318119, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

 SQL Server Execution Times:
   CPU time = 2701 ms,  elapsed time = 256 ms.

 SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 0 ms.

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