//先来看看我们碰到的问题，再来求解答
SQL脚本执行失败,[FireDAC][Phys][MSSQL]-310. Cannot execute command returning result sets. Hint: use Open method for SELECT-like commands
在执行 ExecSQL之前，代码中增加此句可解决问题 （ FDQuery1.Command.CommandKind:=skUpdate; ）
Problem getting FireDAC to execute a query with Common Table Expressions
I was writing some queries to crunch data to export to a spreadsheet for some users. Since I was flattening out the data into a non-normal form, I had some queries that would apply some redundant aggregate counts and averages to every occurrence of an employee in the dataset. These queries used SQL Server Common Table Expressions (CTE) to build a temporary named result set of aggregate data to join to my primary data in order to update it. These queries ran great from SQL Server Management Studio.
When I would try to run them from the utility I was writing, FireDAC appears to be confused by the syntax. If I ran the query using ExecSQL it would return the error message:
[FireDAC][Phys][MSSQL]-310. Cannot execute command returning result sets.
Hint: use Open method for SELECT-like commands.
If I followed the advice of the error message and used OpenOrExecute it would return the error message:
[FireDAC][Phys][MSSQL]-310. Cannot open / define command, which does not return result sets.
Hint: use Execute / ExecSQL method for non-SELECT commands.
I tried every variation of using a TFDQuery or a direct execute from a TFDConnection that I could think of. But FireDAC would always return one of the two error messages above.
The specific query that I was running is as follows:
WITH MED_AVG_CTE AS
(
SELECT EMPLOYEE_NBR, AVG(MEDIAN_PERCENT) AS MED_AVG
FROM TEMP_CAD_ONS_HIT_RATE
WHERE MEDIAN_PERCENT IS NOT NULL
GROUP BY EMPLOYEE_NBR
)
UPDATE TEMP_CAD_ONS_HIT_RATE
SET MEDIAN_AVERAGE = MED_AVG
FROM MED_AVG_CTE
WHERE TEMP_CAD_ONS_HIT_RATE.EMPLOYEE_NBR = MED_AVG_CTE.EMPLOYEE_NBR
This query uses a SELECT statement with an AVG function to create a CTE result set called MED_AVG_CTE. Then it does an UPDATE by joining this newly created CTE to the data that I'm currently crunching. So while this command does have a SELECT - FROM - WHERE statement in it, it is a pure update command / action query that does not return a result set.
After beating my head against a wall for a day on this, I finally came up with a workable hack by sticking in a "OUTPUT DELETED.MEDIAN" line to explicitly make the update command return a result set of a single field of data that I simply ignore. I can now execute the update using an OpenOrExecute() command.
WITH MED_AVG_CTE AS
(
SELECT EMPLOYEE_NBR, AVG(MEDIAN_PERCENT) AS MED_AVG
FROM TEMP_CAD_ONS_HIT_RATE
WHERE MEDIAN_PERCENT IS NOT NULL
GROUP BY EMPLOYEE_NBR
)
UPDATE TEMP_CAD_ONS_HIT_RATE
SET MEDIAN_AVERAGE = MED_AVG
OUTPUT DELETED.MEDIAN -- Result set created here
FROM MED_AVG_CTE
WHERE TEMP_CAD_ONS_HIT_RATE.EMPLOYEE_NBR = MED_AVG_CTE.EMPLOYEE_NBR
My question is: Is there any way to submit an SQL statement to a server where FireDAC will not try and inspect the command being run to determine whether it returns a result set or is an action query? I want FireDAC to simply submit what I tell it to run without question (or error). Is there a flag, property, or method parameter that I'm missing somewhere? Or is this simply a case where FireDAC can't be expected to understand all the various syntax options of all the databases it connects to?
Thanks for any help or insight you might have.
 |
0 |  |
Darryl
embarcadero.delphi.firedac
822 articles.
2 followers.
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Set FDQuery.Command.CommandKind to skUpdate before calling ExecSQL.
--
With best regards,
Dmitry Arefiev / FireDAC Architect
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-1 | |
Dmitry
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