SQL + JQL Plugin. Date difference

[Алексей Терещенко]

query 

SELECT 
KEY(JQL.ISSUE) as "Issue", 
CREATED(JQL.ISSUE) as "Created",
CF(JQL.ISSUE, 11201) as "Closed",
(CF(JQL.ISSUE, 11201) - CREATED(JQL.ISSUE)) as t
FROM JQL
WHERE JQL.QUERY = ' type="_task_" AND "_custom_field_date_" >= startOfMonth()'

returns an error: 

Feature not supported: "VARCHAR - TIMESTAMP"

But the custom field CF(JQL.ISSUE, 11201) is of type Date! 

Help with fix this error! Does anyone know a solution?

[Алексей Терещенко · Accepted solution]

I found a solution:

SELECT 
KEY(JQL.ISSUE) as "Issue", 
CREATED(JQL.ISSUE) as "Created",
CF(JQL.ISSUE, 11201) as "Closed",
DATEDIFF('day', CREATED(JQL.ISSUE), CF(JQL.ISSUE, 11201)) as "DiffDate"
FROM JQL
WHERE JQL.QUERY = ' type="_task_" AND "_custom_field_date_" >= startOfMonth()'