Article ID: 120108
Article Last Modified on 7/27/2001
APPLIES TO
- Microsoft Open Database Connectivity 1.0
This article was previously published under Q120108
BUG# ODBCDBASE: 2147 (1.01.1928)
SYMPTOMS
Calling SQLExecute, SQLFetch, and SQLFreeStmt/SQL_CLOSE in a loop on a prepared statement can cause SQLExecute to return SQL_ERROR after several iterations. The exact number of iterations before this error occurs depends on the number of columns in the table. Users of MFC Database classes note that CRecordSet::Requery followed by CRecordSet::MoveNext in a loop can cause the same behavior.
To produce the problem, do the following with the ODBC dBASE driver:
create table test (col1 char(5), col2 char(5))
SQLPrepare: select * from test order by col2
Loop
SQLExecute
SQLFetch
SQLFreeStmt/SQL_CLOSE
End Loop
At the 925th iteration of the above loop, SQLExecute will fail with SQL_ERROR.
Calling SQLError will return SQL_NO_DATA_FOUND. The number of iterations before failure is dependent on the number of columns in the table. Here is some data that will provide a rough idea of this dependency:
Table with Iterations to SQL_ERROR
-----------------------------------------------------
2 columns, 1 row 925
2 columns, 1000 rows 925
6 columns, 1000 rows 919
10 columns, 1000 rows 599
15 columns, 1000 rows 476
17 columns, 1000 rows 399
19 columns, 1000 rows 393
MFC Database class users will see the same behavior with the following loop, after the same number of iterations as above:
CRecordSet::Open, szSQLStr = select * from test order by col2
Begin Loop
CRecordSet::Requery
CRecordSet::MoveNext
End Loop
WORKAROUND
Making either of the following two changes will work around the problem:
- Remove the ORDER BY in the above SELECT statement (this is applicable to MFC users).
- Do SQLExecDirect instead of SQLPrepare/SQLExecute. (This is not applicable to MFC users.)
STATUS
Microsoft has confirmed this to be a problem in ODBC dBASE Driver version 1.01.1928. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.
Additional query words: 1.01.1928 Desktop Database Drivers Simba MSVC Visual C++
Keywords: kbbug KB120108
