Iterate through temporary table columns to select them - sql

Question

I have a final temporary table (#tempTable) with unknown columns number.
My final select is like this, it works :
SELECT temp.* FROM #tempTable temp
But instead of a '*' I would like to call each columns individually :
SELECT temp.col1, temp.col2 FROM #tempTable temp
To do so I need to iterate through my columns names and create a procedure, I tried something like this :
DECLARE #ColName VARCHAR(255)
SELECT #ColName = min(name) FROM tempdb.sys.columns
WHERE object_id = Object_id('tempdb..#TEMPTABLE');
WHILE #ColName is not null
BEGIN
-- i need to do it all in once and not each time....
declare #sql varchar(max) = 'SELECT tp.'+'#COlName'+'FROM #TEMPTABLE tp'
exec(#sql)
-- Increment the value, how to go to next column ?
select #ColName = min(name) FROM tempdb.sys.columns WHERE object_id =
Object_id('tempdb..#TEMPTABLE') > #ColName -- does not work because it is a string (column name)
END

Answer 1

Try this:
DECLARE #ColName VARCHAR(2000) = 'select '
SELECT #ColName = #ColName + ' temp.' + name + ',' FROM tempdb.sys.columns
WHERE object_id = Object_id('tempdb..#TEMPTABLE')
--delete last character, which is comma and append table name
#ColName = substring(#ColName, 1, LEN(#ColName) - 1) + ' from #TEMPTABLE temp'
exec(#ColName)
This query construct whole table list combined in select ... from ... statement. I increased size of the varchar variable, so it can accomodate long queries.
Also, IMO variable name such as #sql or #query would be more meaningful.

Answer 2

A set based approach
IF OBJECT_ID('tempdb..#TEMPTABLE','U') IS NOT NULL
DROP TABLE #TEMPTABLE;
CREATE TABLE #TEMPTABLE (
Id INT IDENTITY(1,1)
,Col1 INT
,Col2 BIGINT
,Col3 BIGINT
,Col4 DATETIME
,Col5 DATETIME
) ;
DECLARE #SQL NVARCHAR(MAX)
SELECT #SQL = N'SELECT ' + SUBSTRING((
SELECT N', temp.' + S.name
FROM
tempdb.sys.columns S
WHERE
S.object_id = OBJECT_ID('tempdb..#TEMPTABLE')
ORDER BY
S.column_id
FOR XML PATH('')
)
,2
,200000
) + N' FROM #TEMPTABLE temp'
EXEC sys.sp_executesql #SQL