SQL Check if ungroup column values match - sql

Question

I have a sql table with following values
| col1 | col2| source | values
| 1 | 2 | A | null
| 1 | 2 | B | 1.0
| 1 | 2 | C | null
| 1 | 4 | A | 2.0
| 1 | 4 | B | 2.0
| 1 | 4 | C | 2.0
| 1 | 5 | A | null
| 1 | 5 | B | null
| 1 | 5 | C | null
How can I get an output with a group by of col1 and col2 with a flag:
all values match for a group ( flag = 1)
all values are null ( flag = 2)
some values is null (flag = 3)
Output:
| col1 | col2| flag
| 1 | 2 | 3
| 1 | 4 | 1
| 1 | 5 | 2

Answer 1

Or: based on your updated question:
SELECT
col1,
col2,
SUM(CASE WHEN SomeConditionHere THEN 1 ELSE 0 END) AS Flag
FROM Table1
GROUP BY col1, col2;
SQL Fiddle Demo
This will give you:
| COL1 | COL2 | FLAG |
----------------------
| 1 | 2 | 2 |
| 1 | 4 | 0 |
| 1 | 5 | 3 |
Note that: I assumed that the flag is how many NULL values are in the VALUES column, so I used "Values" IS NULL instead of SomeConditionHere.
I couldn't understand how the flag should be computed in the expected results you posted. You have to use the predicate that define your flag instead of "Values" IS NULL.
Update:
Try this:
WITH Flags
AS
(
SELECT
col1, col2,
COUNT(*) ValuesCount,
SUM(CASE WHEN "Values" IS NULL THEN 1 ELSE 0 END) AS NULLValues
FROM Table1
GROUP BY col1, col2
)
SELECT
col1,
col2,
Flag = CASE WHEN ValuesCount = NULLValues THEN 2
WHEN NULLVALUES = 0
AND ValuesCount = (SELECT COUNT(*)
FROM Table1 t2
WHERE t1.col1 = t2.col1
AND t1.col2 = t2.col2) THEN 1
ELSE 3
END
FROM Flags t1;
Updated SQL Fiddle Demo
This will give you:
| COL1 | COL2 | FLAG |
----------------------
| 1 | 2 | 3 |
| 1 | 4 | 1 |
| 1 | 5 | 2 |

Answer 2

In SQLServer2005+
;WITH cte AS
(
SELECT col1, col2, [values],
COUNT(CASE WHEN [values] IS NULL THEN 1 END) OVER(PARTITION BY col1, col2) AS cntNULL,
COUNT(*) OVER(PARTITION BY col1, col2) AS cntCol
FROM dbo.test5
)
SELECT col1, col2, MAX(CASE WHEN cntNULL = 0 THEN 1
WHEN cntNULL = cntCol THEN 2
ELSE 3 END) AS flag
FROM cte
GROUP BY col1, col2
Demo on SQLFiddle

Answer 3

...And solution without CTE if you want more portable SQL:
select col1,
col2,
case
when DistinctValuesWithoutNulls = 1 and NullCount = 0 then 1
when DistinctValuesWithoutNulls = 0 then 2
when NullCount > 0 then 3
end flag
from
(
select col1,
col2,
count(distinct [values]) DistinctValuesWithoutNulls,
sum(case when [values] is null then 1 else 0 end) NullCount
from Table1
group by col1, col2
) tmp