Selecting columns from a query - sql

Question

I'm using a request to get a collection of columns name:
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE [...]
From this collection, I'd like to count every not null, not empty value from the original table group by column name.
Let's say I have a table containing
COL1 | COL2 | COL3
------------------
VAL1 | VAL2 | NULL
VAL3 | | VAL4
VAL5 | |
I'm looking for a request to get:
COL1 | 3
COL2 | 1
COL2 | 1
It's for analytics purpose.
Thanks for your help!

Answer 1

Here is a simple process. Run the following query:
SELECT 'SELECT ''' + COLUMN_NAME + ''', COUNT(['+COLUMN_NAME']) as NotNull FROM [' +SCHEMA_NAME+ '].['+TABLE_NAME+ '] union all '
FROM INFORMATION_SCHEMA.COLUMNS
WHERE [...]
Copy the results into a query window, remove the final union all, and run the query.

Answer 2

The below code seems to work for your issue
create table sample
(
col1 varchar(10),
col2 varchar(10),
col3 varchar(10)
)
INSERT INTO sample (COL1,COL2,COL3) VALUES ('VAL1 ',' VAL2 ',NULL);
INSERT INTO sample (COL1,COL2,COL3) VALUES ('VAL3 ',' ',' VAL4');
INSERT INTO sample (COL1,COL2,COL3) VALUES ('VAL5 ',' ',' ');
DECLARE #cols1 NVARCHAR(MAX);
DECLARE #sql NVARCHAR(MAX);
SELECT #cols1 = STUFF((
SELECT ', COUNT(CASE WHEN len(['+ t1.NAME + '])!=0 THEN 1 END) AS ' + t1.name
FROM sys.columns AS t1
WHERE t1.object_id = OBJECT_ID('sample')
--ORDER BY ', COUNT([' + t1.name + ']) AS ' + t1.name
FOR XML PATH('')
), 1, 2, '');
SET #sql = '
SELECT ' + #cols1 + '
FROM sample
'
EXEC(#sql)

Answer 3

Hereis my little longer take on this:
declare #cols table (colID integer, colName varchar(50))
declare #results table (colName nvarchar(50), valueCount bigint)
-- table name
declare #tableName nvarchar(50) = 'INSERT TABLE NAME HERE'
-- select column names from table
insert into #cols
select column_id, name from sys.columns where object_id = object_id(#tableName) order by column_id
declare #currentColID int = 0
declare #currentName nvarchar(50) = ''
declare #currentCount bigint = 0
declare #sql nvarchar(max) -- where the dynamic sql will be stored
-- go through all columns
while (1 = 1)
begin
-- step by id
select top 1 #currentColID = c.colID, #currentName = c.colName from #cols c
where c.colid > #currentColID order by c.colID
if ##ROWCOUNT = 0 break;
-- dynamic query to get non-empty, not-null counts
select #sql = 'select #p1=COUNT(' + #currentName + ') from ' + #tableName +
' where ' + #currentName + ' is not null or LEN(' + #currentName + ') > 0'
exec sp_executesql #sql, N'#p1 bigint output', #p1 = #currentCount output
-- insert result to buffer
insert into #results values (#currentName, #currentCount)
end
-- print the buffer
select * from #results
Have fun :)