sql sql-server count sql-server-2012 subquery

How do I count subquery CASE WHEN categories with an outer query?

I have a sample set of data in this db<>fiddle. The data represents a batch of wells that fall into different well-type categories based on some criteria. I am trying to group the wells by the category they fall into and then count how many wells are in each category based on another set of criteria.

My current query partially works but only correctly counts wells that are higher in the CASE WHEN clause hierarchy. This is because the first CASE WHEN has the chance to assign well categories to all of the wells in the data set. However, as it goes through each CASE WHEN clause, the query "see's" fewer wells because it runs out of wells it can assign a category to. By the time it reaches the end, almost all of the wells have already had a category assigned to them, preventing some category counts from occurring at all.

Here is the current query I have, which is also in the db<>fiddle link above:

SELECT
    dt.WellCategory,
    ISNULL(SUM(CASE WHEN dt.LeaseType IN ('F','I','S','P') OR dt.LeaseType NOT IN ('F', 'I', 'S', 'P', 'U') THEN 1 END), 0) AS [Number of Wells], -- Federal + Indian + State + Fee + Multi-Lease
    ISNULL(SUM(CASE WHEN dt.LeaseType = 'F' THEN 1 END), 0) AS [Federal], -- Sums up how many wells from the subquery have a leasetype of "Federal"
    ISNULL(SUM(CASE WHEN dt.LeaseType = 'I' THEN 1 END), 0) AS [Indian],
    ISNULL(SUM(CASE WHEN dt.LeaseType = 'S' THEN 1 END), 0) AS [State],
    ISNULL(SUM(CASE WHEN dt.LeaseType = 'P' THEN 1 END), 0) AS [Fee (Private)],
    ISNULL(SUM(CASE WHEN dt.LeaseType NOT IN ('F', 'I', 'S', 'P', 'U') THEN 1 END), 0) AS [Multiple Lease Types]
FROM
(
    SELECT -- Subquery labels wells according to their wellstatus, welltype, etc.
        c.LeaseType,
        CASE 
            WHEN w.WellStatus = 'p' AND w.WellType = 'gw' OR ((w.WellStatus = 'pai' OR w.WellStatus = 'pii') AND (w.WellType = 'gwi' OR w.WellType = 'ggi' OR w.WellType = 'gwd')) THEN 'Producing Gas Wells'
            WHEN w.WellStatus = 'p' AND w.WellType = 'ow' OR ((w.WellStatus = 'pai' OR w.WellStatus = 'pii') AND (w.WellType = 'owi' OR w.WellType = 'ogi' OR w.WellType = 'owd')) THEN 'Producing Oil Wells'
            WHEN w.WellStatus = 's' AND w.WellType = 'ow' OR ((w.WellStatus = 'sai' OR w.WellStatus = 'sii') AND (w.WellType = 'owi' OR w.WellType = 'ogi' OR w.WellType = 'owd')) THEN 'Shut-In Oil Wells'
            WHEN w.WellStatus = 's' AND w.WellType = 'gw' OR ((w.WellStatus = 'sai' OR w.WellStatus = 'sii') AND (w.WellType = 'gwi' or w.WellType = 'ggi' or w.WellType = 'gwd')) THEN 'Shut-In Gas Wells'
            WHEN w.WellStatus = 'a' AND w.WellType = 'wi' THEN 'Active Water Injection Wells'
            WHEN w.WellStatus = 'a' AND w.WellType = 'gi' THEN 'Active Gas Injection Wells'
            WHEN w.WellStatus = 'a' AND w.WellType = 'wd' THEN 'Active Water Disposal Wells'
            WHEN w.WellStatus = 'a' AND w.WellType = 'gs' THEN 'Active Gas Storage Wells'
            WHEN w.WellStatus = 'a' AND w.WellType = 'ws' THEN 'Active Water Source Wells'
            WHEN w.WellStatus = 'a' AND w.WellType = 'tw' THEN 'Active Test Holes'
            WHEN w.WellStatus = 'i' AND w.WellType = 'wi' THEN 'Inactive Water Injection Wells'
            WHEN w.WellStatus = 'i' AND w.WellType = 'gi' THEN 'Inactive Gas Injection Wells'
            WHEN w.WellStatus = 'i' AND w.WellType = 'wd' THEN 'Inactive Water Disposal Wells'
            WHEN w.WellStatus = 'i' AND w.WellType = 'gs' THEN 'Inactive Gas Storage Wells'
            WHEN w.WellStatus = 'i' AND w.WellType = 'ws' THEN 'Inactive Water Source Wells'
            WHEN w.WellStatus = 'i' AND w.WellType = 'tw' THEN 'Inactive Test Holes'
            WHEN w.WellStatus = 'ta' THEN 'Temporarily-Abandoned Wells'
            WHEN w.WellStatus = 'pa' THEN 'Plugged and Abandoned Wells'
            WHEN c.LateralStatus = 'NEW' THEN 'New Permits - Not Yet Approved'
            WHEN c.LateralStatus = 'APD' THEN 'Permits Approved - Not Yet Commenced'
            WHEN c.LateralStatus = 'DRL' THEN 'Drilling Commenced - Not Yet Completed'
            WHEN c.LateralStatus = 'OPS' THEN 'Drilling Operations Suspended'
            WHEN w.WellStatus IN ('drl','ops','p','s','ta','pai','pii','sai','sii','a','i') AND w.Operator = 101600 THEN 'Open Orphan Wells (no known operator)'
            WHEN w.WellStatus IN ('drl','ops') THEN 'Total Holes Not Yet Completed'
            WHEN ((w.WellStatus = 'p' or w.WellStatus = 's') AND w.WellType <> 'LI') OR (w.WellStatus = 'pai' OR w.WellStatus = 'pii' OR w.WellStatus = 'sai' OR w.WellStatus = 'sii') THEN 'Total Wells Capable of Production'
            WHEN (w.WellStatus = 'drl' OR w.WellStatus = 'ops' OR ((w.WellStatus = 'p' or w.WellStatus = 's') AND w.WellType <> 'LI') OR w.WellStatus = 'ta' OR w.WellStatus = 'pai' OR w.WellStatus = 'pii' OR w.WellStatus = 'sai' OR w.WellStatus = 'sii' OR w.WellStatus = 'a' OR w.WellStatus = 'i') THEN 'Total Non-Plugged Wells'
            WHEN (w.WellStatus = 'drl' or w.WellStatus = 'ops' or ((w.WellStatus = 'p' or w.WellStatus = 's') and w.WellType <> 'LI') or w.WellStatus = 'ta' or w.WellStatus = 'pai' or w.WellStatus = 'pii' or w.WellStatus = 'sai' or w.WellStatus = 'sii' or w.WellStatus = 'a' or w.WellStatus = 'i' or w.WellStatus = 'pa') THEN 'Total Wells Drilled'
        END AS WellCategory
    FROM HWell w
        LEFT JOIN HConstruct c ON c.WellKey = w.PKey
) dt
GROUP BY dt.WellCategory
ORDER BY dt.WellCategory DESC

Here is the table the query above produces:

Table #1

WellCategory	Number of Wells	Federal	Indian	State	Fee (Private)	Multiple Lease Types
Total Wells Capable of Production	2	2	0	0	0	0
Temporarily-Abandoned Wells	1	1	0	0	0	0
Shut-In Oil Wells	21	10	10	0	1	0
Shut-In Gas Wells	26	19	2	4	1	0
Producing Oil Wells	59	18	25	6	10	0
Producing Gas Wells	90	59	1	25	5	0
Plugged and Abandoned Wells	113	60	15	19	19	0
Permits Approved - Not Yet Commenced	14	4	2	2	4	2
New Permits - Not Yet Approved	1	0	1	0	0	0
Inactive Water Injection Wells	18	11	5	2	0	0
Drilling Operations Suspended	4	1	3	0	0	0
Drilling Commenced - Not Yet Completed	4	1	1	0	2	0
Active Water Injection Wells	6	1	5	0	0	0
Active Water Disposal Wells	1	0	0	1	0	0
NULL	140	83	28	14	15	0

Here is the table I know the same data set can produce and the one I want to replicate:

Table #2

Well Statuses	Number Of Wells	Federal	Indian	State	Fee (Private)	Multiple Lease Types
Producing Oil Wells	59	18	25	6	10	0
Producing Gas Wells	90	59	1	25	5	0
Shut-In Oil Wells	21	10	10	0	1	0
Shut-In Gas Wells	26	19	2	4	1	0
Active Water Injection Wells	6	1	5	0	0	0
Active Gas Injection Wells	0	0	0	0	0	0
Active Water Disposal Wells	1	0	0	1	0	0
Active Gas Storage Wells	0	0	0	0	0	0
Active Water Source Wells	0	0	0	0	0	0
Active Test Holes	0	0	0	0	0	0
Inactive Water Injection Wells	18	11	5	2	0	0
Inactive Gas Injection Wells	0	0	0	0	0	0
Inactive Water Disposal Wells	0	0	0	0	0	0
Inactive Gas Storage Wells	0	0	0	0	0	0
Inactive Water Source Wells	0	0	0	0	0	0
Inactive Test Holes	0	0	0	0	0	0
Temporarily-Abandoned Wells	1	1	0	0	0	0
Plugged and Abandoned Wells	113	60	15	19	19	0
New Permits - Not Yet Approved	1	0	1	0	0	0
Permits Approved - Not Yet Commenced	14	4	2	2	4	2
Drilling Commenced - Not Yet Completed	4	1	1	0	2	0
Drilling Operations Suspended	4	1	3	0	0	0
Open Orphan Wells (no known operator)	1	1	0	0	0	0
Total Holes Not Yet Completed	8	2	4	0	2	0
Total Wells Capable of Production	198	108	38	35	17	0
Total Non-Plugged Wells	232	123	52	38	19	0
Total Wells Drilled	345	183	67	57	38	0

Table #2 is generated using a much longer query that uses several subqueries and temp tables to count how many wells belong to each category using their DISTINCT w.WellID. In addition, the full data set has a lot more entries, usually each category has at least some wells in it and not so many "0's".

I don't know how to tell the query to count wells more than once if they fall into several well categories without making the query super long and start introducing temp tables, which I would prefer not to do. *NOTE I do not want to count a well twice for same category, only count it once per category.

Solution

Here's one way you could do it while keeping it somewhat easy to read:

I broke the CASE statement into logical pieces. Parts that don't overlap but seem related go into their own query to determine the category. Then I UNION ALL them together to avoid de-duping.

There's tons of ways this could be done, and this is just one of them...

Also, like I mentioned in the chat session, if you are able to, I would highly recommend working on normalizing this data, creating lookup tables, etc.

WITH cte_Wells AS (
    SELECT w.WellStatus, w.WellType, c.LateralStatus, c.LeaseType, w.Operator
    FROM dbo.HWell w
        LEFT JOIN dbo.HConstruct c ON c.WellKey = w.PKey
)
SELECT
    dt.WellCategory,
    ISNULL(SUM(CASE WHEN dt.LeaseType IN ('F','I','S','P') OR dt.LeaseType NOT IN ('F', 'I', 'S', 'P', 'U') THEN 1 END), 0) AS [Number of Wells], -- Federal + Indian + State + Fee + Multi-Lease
    ISNULL(SUM(CASE WHEN dt.LeaseType = 'F' THEN 1 END), 0) AS [Federal], -- Sums up how many wells from the subquery have a leasetype of "Federal"
    ISNULL(SUM(CASE WHEN dt.LeaseType = 'I' THEN 1 END), 0) AS [Indian],
    ISNULL(SUM(CASE WHEN dt.LeaseType = 'S' THEN 1 END), 0) AS [State],
    ISNULL(SUM(CASE WHEN dt.LeaseType = 'P' THEN 1 END), 0) AS [Fee (Private)],
    ISNULL(SUM(CASE WHEN dt.LeaseType NOT IN ('F', 'I', 'S', 'P', 'U') THEN 1 END), 0) AS [Multiple Lease Types]
FROM (
    SELECT w.LeaseType, x.WellCategory
    FROM cte_Wells w
        CROSS APPLY (
            SELECT WellCategory = CASE 
                                    WHEN w.WellStatus = 'p' AND w.WellType = 'gw' OR (w.WellStatus IN ('pai','pii') AND w.WellType IN ('gwi','ggi','gwd')) THEN 'Producing Gas Wells'
                                    WHEN w.WellStatus = 'p' AND w.WellType = 'ow' OR (w.WellStatus IN ('pai','pii') AND w.WellType IN ('owi','ogi','owd')) THEN 'Producing Oil Wells'
                                    WHEN w.WellStatus = 's' AND w.WellType = 'gw' OR (w.WellStatus IN ('sai','sii') AND w.WellType IN ('gwi','ggi','gwd')) THEN 'Shut-In Gas Wells'
                                    WHEN w.WellStatus = 's' AND w.WellType = 'ow' OR (w.WellStatus IN ('sai','sii') AND w.WellType IN ('owi','ogi','owd')) THEN 'Shut-In Oil Wells'
                                    WHEN w.WellStatus = 'a' AND w.WellType = 'wi' THEN 'Active Water Injection Wells'
                                    WHEN w.WellStatus = 'a' AND w.WellType = 'gi' THEN 'Active Gas Injection Wells'
                                    WHEN w.WellStatus = 'a' AND w.WellType = 'wd' THEN 'Active Water Disposal Wells'
                                    WHEN w.WellStatus = 'a' AND w.WellType = 'gs' THEN 'Active Gas Storage Wells'
                                    WHEN w.WellStatus = 'a' AND w.WellType = 'ws' THEN 'Active Water Source Wells'
                                    WHEN w.WellStatus = 'a' AND w.WellType = 'tw' THEN 'Active Test Holes'
                                    WHEN w.WellStatus = 'i' AND w.WellType = 'wi' THEN 'Inactive Water Injection Wells'
                                    WHEN w.WellStatus = 'i' AND w.WellType = 'gi' THEN 'Inactive Gas Injection Wells'
                                    WHEN w.WellStatus = 'i' AND w.WellType = 'wd' THEN 'Inactive Water Disposal Wells'
                                    WHEN w.WellStatus = 'i' AND w.WellType = 'gs' THEN 'Inactive Gas Storage Wells'
                                    WHEN w.WellStatus = 'i' AND w.WellType = 'ws' THEN 'Inactive Water Source Wells'
                                    WHEN w.WellStatus = 'i' AND w.WellType = 'tw' THEN 'Inactive Test Holes'
                                    WHEN w.WellStatus = 'ta' THEN 'Temporarily-Abandoned Wells'
                                    WHEN w.WellStatus = 'pa' THEN 'Plugged and Abandoned Wells'
                                    ELSE NULL
                                END
        ) x
    WHERE x.WellCategory IS NOT NULL
    -----------------
    UNION ALL
    -----------------
    SELECT w.LeaseType, x.WellCategory
    FROM cte_Wells w
        CROSS APPLY (
            SELECT WellCategory = CASE 
                                    WHEN w.LateralStatus = 'NEW' THEN 'New Permits - Not Yet Approved'
                                    WHEN w.LateralStatus = 'APD' THEN 'Permits Approved - Not Yet Commenced'
                                    WHEN w.LateralStatus = 'DRL' THEN 'Drilling Commenced - Not Yet Completed'
                                    WHEN w.LateralStatus = 'OPS' THEN 'Drilling Operations Suspended'
                                    ELSE NULL
                                END
        ) x
    WHERE x.WellCategory IS NOT NULL
    -----------------
    UNION ALL
    -----------------
    SELECT w.LeaseType, WellCategory = 'Open Orphan Wells (no known operator)'
    FROM cte_Wells w
    WHERE w.WellStatus IN ('drl','ops','p','s','ta','pai','pii','sai','sii','a','i') AND w.Operator = 101600
    -----------------
    UNION ALL
    -----------------
    SELECT w.LeaseType, WellCategory = 'Total Holes Not Yet Completed'
    FROM cte_Wells w
    WHERE w.WellStatus IN ('drl','ops')
    -----------------
    UNION ALL
    -----------------
    SELECT w.LeaseType, WellCategory = 'Total Wells Capable of Production'
    FROM cte_Wells w
    WHERE (w.WellStatus IN ('p','s') AND w.WellType <> 'LI') OR w.WellStatus IN ('pai','pii','sai','sii')
    -----------------
    UNION ALL
    -----------------
    SELECT w.LeaseType, WellCategory = 'Total Non-Plugged Wells'
    FROM cte_Wells w
    WHERE (w.WellStatus IN ('p','s') AND w.WellType <> 'LI') OR w.WellStatus IN ('drl','ops','ta','pai','pii','sai','sii','a','i')
    -----------------
    UNION ALL
    -----------------
    SELECT w.LeaseType, WellCategory = 'Total Wells Drilled'
    FROM cte_Wells w
    WHERE (w.WellStatus IN ('p','s') AND w.WellType <> 'LI') or w.WellStatus IN ('drl','ops','ta','pai','pii','sai','sii','a','i','pa')
) dt
GROUP BY dt.WellCategory
ORDER BY dt.WellCategory DESC

I've checked the results of this query against your sample data and proposed expected results, and they appear to match. So this will get you what you want. However, since I don't know the data, you'll need to inspect it for logic errors, and performance.

NOTE: The results of this query do not produce counts for empty categories. If that is something you need, then comment on this solution and I can fix it. The fix is to add a table with all categories, then LEFT JOIN to that the results of the counts.