MySQL Bugs: #82604: LINQ conditional Group By column excluded from select list

Bug #82604	LINQ conditional Group By column excluded from select list
Submitted:	17 Aug 2016 3:41	Modified:	17 Aug 2016 6:36
Reporter:	Brian Tacker	Email Updates:
Status:	Duplicate	Impact on me:	None
Category:	Connector / NET	Severity:	S3 (Non-critical)
Version:	6.9.9	OS:	Windows
Assigned to:		CPU Architecture:	Any
Tags:	linq

Description:
When doing a LINQ statement with a conditional group by, the group by column is not included in the SELECT list.

How to repeat:
The following LINQ statement:

from trans in Transaction
group trans by new { GroupCol = (groupByDate ? trans.Date : trans.StoreId) } into g1
select new { Group = g1.Key.GroupCol, Count = g1.Count() }

Will produce the following SQL:

SELECT
1 AS `C1`, 
`GroupBy1`.`K1` AS `C2`, 
`GroupBy1`.`A1` AS `C3`
FROM (SELECT
COUNT(1) AS `A1`
FROM `Transactions` AS `Extent1`
 GROUP BY 
CASE WHEN (@p__linq__0 = 1) THEN (`Extent1`.`Date`)  ELSE (`Extent1`.`StoreId`) END) AS `GroupBy1`

When this SQL is run, you get "Unknown column 'GroupBy1.K1' in 'field list'"

Suggested fix:
Producing the following SQL gives the desired result:

SELECT
1 AS `C1`, 
`GroupBy1`.`K1` AS `C2`, 
`GroupBy1`.`A1` AS `C3`
FROM (SELECT
CASE WHEN (@p__linq__0 = 1) THEN (`Extent1`.`Date`)  ELSE (`Extent1`.`StoreId`) END AS `K1`,
COUNT(1) AS `A1`
FROM `Transactions` AS `Extent1`
 GROUP BY 
`K1`) AS `GroupBy1`

Hello Brian Tacker,

Thank you for the bug report.
This is most likely duplicate of Bug #79817, please see Bug #79817.

Thanks,
Chiranjeevi.

Dear support,

any updates on this issue? Is there a workaround available?
Thank you very much!
BR Chris

Workaround: use myGroup.Min(f => f.x) instead of myGroup.Key.x