How to dynamically calculate the sums of many columns in a GROUP? - sql

Question

In the table below, I have a variable number of columns, and that number is in the 1000s. I need to sum all the values of each of the 1000 columns grouped by the person's name. So, smith's total test_score_1, total test_score_2,...total test_score_1000. And then Jackson's total test_score_1, total test_score_2,...total test_score_1000.
I don't know the number of 'test_score_n' columns beforehand and they are always changing.
So given this table:
name test_score_1 test_score_2 ... test_score_1000
smith 2 1 0
jackson 0 3 1
jackson 1 1 2
jackson 3 0 3
smith 4 5 1
How can I produce the table below?
name test_score_1 test_score_2 ... test_score_1000
smith 6 6 1
jackson 4 4 6

Answer 1

SQL to generate the SQL
DECLARE #generatedSQL nvarchar(max);
SET #generatedSQL = (
SELECT
'SELECT ' +
SUBSTRING(X.foo, 2, 2000) +
'FROM ' +
QUOTENAME(SCHEMA_NAME(t.schema_id)) + '.' + QUOTENAME(t.name) +
' GROUP BY name' --fix this line , edited
FROM
sys.tables t
CROSS APPLY
(
SELECT
', SUM(' + QUOTENAME(c.name) + ')'
FROM
sys.columns c
WHERE
c.object_id = t.object_id
AND
c.name <> 'Name'
FOR XML PATH('')
) X (foo)
WHERE
t.name = 'MyTable'
);
EXEC (#generatedSQL);

Answer 2

Demo: http://rextester.com/MAFCP19297
SQL
DECLARE #cols varchar(max), #sql varchar(max);
SELECT #cols =
COALESCE(#cols + ', ', '') + 'SUM(' + COLUMN_NAME + ') AS ' + COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = '<tbl name>'
AND COLUMN_NAME <> 'name'
-- The AND below may be optional - see "Additional Notes #1"
AND TABLE_CATALOG = '<database schema name>';
SET #sql = 'SELECT name, ' + #cols + ' FROM tbl GROUP BY name;';
EXEC (#sql);
Explanation
The DECLARE creates two variables - one for storing the column summing part of the SQL and the other for storing the whole dynamically created SQL statement to run.
The SELECT queries the INFORMATION_SCHEMA.COLUMNS system table to get the names of all the columns in tbl apart from the name column. (Alternatively the sys tables could be used - answers to this question discuss the relative merits of each). These row values are then converted into a single comma separated value using this method (which is arguably a little simpler than the alternative FOR XML PATH ('') method). The comma-separated values are a bit more than just the column names - they SUM over each column name and then assign the result with an alias of the same name.
The SET then builds a simple SQL statement that selects the name and all the summed values - e.g: SELECT name, SUM(test_score_1) AS test_score_1, SUM(test_score_2) AS test_score_2, SUM(test_score_1000) AS test_score_1000 FROM tbl GROUP BY name;.
The EXEC then runs the above query.
Additional Notes
If there is a possibility that the table name may not be unique across all databases then the following clause is needed in the select: AND TABLE_CATALOG = '<database schema name>'
My initial answer to this question was mistakenly using MySQL rather than SQL Server - this has now been corrected but the previous version is still in the edit history and might be helpful to someone...

Answer 3

Try this dynamic column generation Sql script
DECLARE #Sql nvarchar(max)
SET #Sql=( SELECT DISTINCT 'SELECT'+
STUFF((SELECT ', '+ ' SUM( '+ COLUMN_NAME +' ) AS '+ QUOTENAME( COLUMN_NAME )
FROM INFORMATION_SCHEMA.COLUMNS Where TABLE_NAME ='Tab1000'
FOR XML PATH (''),type).value('.','varchar(max)'),1,2,'')
+' From Tab1000'From INFORMATION_SCHEMA.COLUMNS Where TABLE_NAME ='Tab1000')
EXEC (#sql)

Answer 4

Try the below script
(set the #tableName= [yourTablename] and #nameColumn to the name of the field you want to group by)
Declare #tableName varchar(50)='totalscores'
Declare #nameColumn nvarchar(50)='name'
Declare #query as nvarchar(MAX) ;
select #query = 'select ' + nameColumn + cast(sumColumns as nvarchar(max)) + 'from ' + #tableName +' group by ' + nameColumn from (
select #nameColumn nameColumn, (SELECT
', SUM(' + QUOTENAME(c.name) + ') ' + QUOTENAME(c.name)
FROM
sys.columns c
WHERE
c.object_id=t.object_id and c.name != #nameColumn
order by c.name
FOR
XML path(''), type
) sumColumns
from sys.tables t where t.name= #tableName
)t
EXECUTE(#query)

Answer 5

Change tablename with your tablename.
Declare #query as nvarchar(MAX) = (SELECT
'SELECT name,' + SUBSTRING(tbl.col, 2, 2000) + ' FROM ' + QUOTENAME(SCHEMA_NAME(t.schema_id)) + '.' + QUOTENAME(t.name) + 'Group By name'
FROM
sys.tables t
CROSS APPLY
(
SELECT
', SUM(' + QUOTENAME(columns.name) + ') as ' + columns.name
FROM
sys.columns columns
WHERE
columns.object_id = t.object_id and columns.name != 'name'
FOR XML PATH('')
) tbl (col)
WHERE
t.name = 'tablename')
select #query EXECUTE(#query)

Answer 6

GBN's dynamic SQL would be my first choice (+1), and would be more performant. However, if you are interested in breaking this horrible cycle of a 1,000+ columns, consider the following:
Example
Declare #YourTable Table ([col 1] int,[col 2] int,[col 1000] varchar(50))
Insert Into #YourTable Values
(2,1,0)
,(4,5,1)
Select Item = replace(C.Item,'_x0020_', ' ')
,Value = sum(C.Value)
From #YourTable A
Cross Apply (Select XMLData= cast((Select A.* for XML RAW) as xml)) B
Cross Apply (
Select Item = a.value('local-name(.)','varchar(100)')
,Value = a.value('.','int')
From B.XMLData.nodes('/row') as C1(n)
Cross Apply C1.n.nodes('./#*') as C2(a)
Where a.value('local-name(.)','varchar(100)') not in ('Fields','ToExclude')
) C
Group By C.Item
Returns
Item Value
col 1 6
col 2 6
col 1000 1