ms access query (ms access freezes)

Question

I have this report and need to add totals for each person (the red circle) existing report

new report

I cannot change the existing report so I export data from MS SQL to MS Access and create a new report there. I got it working for one employee but have trouble with a query which would for multiple employees.

This query extract data use as input:

SELECT [TIME].[RCD_NUM], [TIME].[EMP_ID], [TIME].[PPERIOD], [TIME].[PRUN], [TIME].[TDATE], [TIME].[PC], [TIME].[RATE], [TIME].[HOURS], [TIME].[AMOUNT], [TIME].[JOB_ID], [TIME].[UPDATED], [TIME].[UPDATED_BY], [TIME].[LOG_DATE], [TIME].[ORIGINAL_REC_NUM]
FROM [TIME]
WHERE ((([TIME].[EMP_ID])=376) And (([TIME].[TDATE])<=#12/31/2006# And ([TIME].[TDATE])>=#1/1/2006#) And (([TIME].[PC])<599));

this query populates the report:

SELECT *
FROM TIME1
WHERE RCD_NUM = (SELECT Max(RCD_NUM) FROM [TIME1] UQ WHERE UQ.PPERIOD = [TIME1].PPERIOD AND UQ.PC = [TIME1].PC);

the problem is if I remove EMP_ID from the first query like this

SELECT [TIME].[RCD_NUM], [TIME].[EMP_ID], [TIME].[PPERIOD], [TIME].[PRUN], [TIME].[TDATE], [TIME].[PC], [TIME].[RATE], [TIME].[HOURS], [TIME].[AMOUNT], [TIME].[JOB_ID], [TIME].[UPDATED], [TIME].[UPDATED_BY], [TIME].[LOG_DATE], [TIME].[ORIGINAL_REC_NUM]
FROM [TIME]
WHERE ((([TIME].[TDATE])<=#12/31/2006# And ([TIME].[TDATE])>=#1/1/2006#) And (([TIME].[PC])<599));

then the second query doesn't work and ms access freezes when running this query.

any help/idea please?

Answer 1

Caveat : I won't pretend to know the precise cause of the problem, but I have had to repeatedly refactor queries in Access to get them working even though the original SQL statements are completely valid in regards to syntax and logic. Sometimes I've had to convolute a sequence of queries just to avoid bugs in Access. Access is often rather dumb and will simply (re)execute queries and subqueries exactly as given without optimization. At other times Access will attempt to combine queries by performing some internal optimizations, but sometimes those introduce frustrating bugs. Something as simple as a name change or column reordering can be the difference between a functioning query and one that crashes or freezes Access.

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First consider:

• Can you leave the data on SQL Server and link to the results in Access (rather than export/importing it into Access)? Even if you need or prefer to use Access for creating the actual report, you could use all the power of SQL Server for querying the data--it is likely less buggy and more efficient.
  • Common best practice is to create SQL Server stored procedures that return just what data you need in Access. A pass-through query is created in Access to retrieve the data, but all data operations are performed on the server.
• Perhaps this is just a performance issue where limiting the set by [EMP_ID] selects a small subset, but the full table is large enough to "freeze" Access.
  • How long have you let Access remain frozen before killing the process? Be patient... like many, many minutes (or hours). Start it in the morning and check after lunch. :) It might eventually return a result set. This does not imply it is tolerable or that there is no other solution, but it can be useful to know if it eventually returns data or not.
  • How many possible records are there?
  • Are the imported data properly indexed? Add indexes to all key fields and those which are used in WHERE clauses.
  • Is the database located on a network share or is it local? Try copying the database to a local drive.

Other hints:

• Try the BETWEEN operator for dates in the WHERE clause.

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Try refactoring the "second" query by performing a join in the FROM clause rather than the WHERE clause. In doing this, you may also want to save the subquery as a named query (just as [TIME1] is saved). Whether or not a query is saved or embedded in another statement CAN change the behavior of Access (see caveat) even though the results should be identical.

Here's a version with the embedded aggregate query. Notice how all column references are qualified with the source. Some of the original query's columns do not have a source alias prefixing the column name. Remember the caveat... such picky details can affect Access behavior.:

SELECT TIME1.*
FROM TIME1 INNER JOIN
  (SELECT UQ.PPERIOD, UQ.PC, Max(UQ.RCD_NUM) As Max_RCD_NUM
   FROM [TIME1] UQ
   GROUP BY UQ.PPERIOD, UQ.PC) As TIMEAGG
  ON (TIME1.PPERIOD = TIMEAGG.PPERIOD) And (TIME1.PC = TIMEAGG.PC)
    AND (TIME1.RCD_NUM = TIMEAGG.Max_RCD_NUM)