How to build a WHILE Loop using SQL Server 2014 - sql

Question

I have loaded the column names from a table into the temporary table called #COLUMN_NAMES. I would like to build a while loop that passes each of the rows from the temp table through my #Data_Quality_Check table that I created below.
There are 54 rows of column_names in my table #Column_names currently. Ideally I would like to have the while loop process each of the variables and put the output into the #Data_Quality_Check table.
if object_id('tempdb..#COLUMN_NAMES') is not null
drop table #COLUMN_NAMES
SELECT COLUMN_NAME AS Column_Names
INTO #COLUMN_NAMES
FROM information_schema.columns
WHERE table_name = 'ssrs_sourcedata'
----- >>>> !!!!!! INSERT CODE TO BUILD WHILE LOOP !!!!
if object_id('tempdb..#DATA_QUALITY_CHECK') is not null
drop table #DATA_QUALITY_CHECK
SELECT
periodenddate,
'#Column_Name' AS Label,
MIN(#Column_Name) AS Min_Value,
MAX(#Column_Name) AS Max_Value,
SUM(#Column_Name) AS Sum_Value,
AVG(#Column_Name) AS Avg_Value,
SUM(Case when #Column_Name IS NULL THEN 1 ELSE 0 END) AS Null_Count,
SUM(Case when len(cast(#Column_Name AS VARCHAR)) = 0 THEN 1 ELSE 0 END) AS Space_Count,
MAX(len(cast(#Column_Name AS VARCHAR))) AS max_length,
MIN(len(cast(#Column_Name AS VARCHAR))) AS min_length
INTO
#DATA_QUALITY_CHECK
FROM
dbcrms.report.ssrs_sourcedata
WHERE
periodenddate = '2017-06-30'
GROUP BY
periodenddate

Answer 1

Dynamic that badboy. You need to create the empty temp table first though
declare #cnt int = 1;
declare #mcnt int;
declare #vsql varchar(2000);
declare #column_name varchar(100);
select #mcnt = count(*)
from #COLUMN_NAMES;
while #cnt <= #mcnt
begin
select #column_name = column_names
from
(
select column_names, row_number() over(order by column_names) rn
from #COLUMN_NAMES
)
where rn = #cnt;
set #vsql = 'insert into #DATA_QUALITY_CHECK (Label, min_value, max_value, sum_value, avg_value, null_count, space_count, max_length, min_length)
SELECT periodenddate, ''' + #Column_Name + ''' AS Label,
MIN(' + #Column_Name+ ') AS Min_Value,
MAX(' + #Column_Name + ') AS Max_Value,
SUM(' + #Column_Name + ') AS Sum_Value,
AVG(' + #Column_Name + ') AS Avg_Value,
SUM(Case when ' + #Column_Name + ' IS NULL THEN 1 ELSE 0 END) AS Null_Count,
SUM(Case when len(cast(' + #Column_Name + ' AS VARCHAR)) = 0 THEN 1 ELSE 0 END) AS Space_Count,
MAX(len(cast(' + #Column_Name + ' AS VARCHAR))) AS max_length,
MIN(len(cast(' + #Column_Name + ' AS VARCHAR))) AS min_length
FROM dbcrms.report.ssrs_sourcedata WHERE periodenddate = '2017-06-30'
GROUP BY periodenddate ';
execute(#vsql);
set #cnt = #cnt + 1;
end;