SQLBrowseConnect() & SQLColAttribute()

Question

Hello,
I am writing to you about a series of problems that I have while trying to connect to Oracle 11g through ODBC in a C++ application.
So, first of all, I downloaded Oracle 11g from Oracle’s website. I installed it in a Virtual Machine (Windows XP Professional – 32 bit). The VM is running on a Windows XP Professional x64.
The first problem that I have is using the ODBC SQLBrowseConnect() function.
The context is something like this:
TCHAR szConnect[1024];
TCHAR szResult[1024];
SQLSMALLINT cbRSize = 0;
SQLRETURN retcode = SQL_SUCCESS;
// szConnect has the following value: T(“Oracle in OraOdac11ghome1”);
memset(szResult, 0, sizeof(TCHAR) * 1024);
retcode = ::SQLBrowseConnect(m_hConn, szConnect, SQL_NTS, szResult, 1024, &cbRSize);
The response in szResult should be a list of Oracle servers. I read on a forum that Oracle does not have a broadcast service and reads the information it needs from tsnames.ora. I copied the tsnames.ora from the server (the virtual machine) to the local computer, I figured that at least that server will be listed in the response string. Bad luck!! The only things that I receive in the response list are some properties for the connection. It really does not qualifies as a valid response. Anyway… I kept searching for examples on how to connect to Oracle DB and I saw that the recommended way is through SQLDriverConnect(). I do not understand this thing, because SQLBrowseConnect() should provide the highest level of flexibility. Anyway… I created a little test section in the code to see if SQLDriverConnect() really works. After all the trouble that I had with SQLBrowseConnect() I had serious doubts about anything related to the ODBC implementation in Oracle.
To my surprise, I managed to connect to the Oracle server really quick. I connected with SYSTEM user. But here comes the tricky part.
When running queries from my application I try to get all the information I can from the server.
Example:
TCHAR szQuery[1024];
SQLRETURN retcode = SQL_SUCCESS;
SQLSMALLINT nColCount = 0;
TCHAR szColTableName[1024];
SQLSMALLINT cbColTableName = 0;
memset(szQuery, 0, sizeof(TCHAR) * 1024);
memset(szColTableName, 0, sizeof(TCHAR) * 1024);
tcscpy(szQuery, T(“Select * From Test”)); // Where test is a table with no data, just for test 
// The table is created under SYSTEM schema so… I should be able to get all the info I want
retcode = ::SQLPrepare(m_hStmt, szQuery, SQL_NTS);
// if fails exist from method with appropriate error code
retcode = ::SQLNumResultCols(m_hStmt, &nColCount);
// if fails skip the following for
for(SQLSMALLINT nColIdx = 0; nColIdx < nColCount; nColIdx ++)
retcode = ::SQLColAttribute(m_hStmt, nColIdx, SQL_COL_TABLE_NAME, &szColTableName, 1024, &cbColTableName, NULL);
I expected to see in szColTableName the string “Test”, but guess what the value in szColTableName was after I ran this section of code? Empty!!! And cbColTableName was 0.
In my app I really need the table name, so… created a for with nField from 0 to 50.000 to put as third parameter in SQLColAttribute. I thought that maybe Oracle is using different defines (who knows… strange things do happen there). Nothing. All I could get was the column name and column type. Other than this… NOTHING!!!
Can anyone help me in this issue?
Thanks in advance,
H

Answer 1

Calling SQLDescribeCol I get 19, 22, and 29 for col1, col2, col3 respectively as column size and 0 for decimal digits.
I really should be getting this info by calling SQLColAttribute SQL_DESC_PRECISION but since that does not work for this driver ( DataDirect ODBC Driver for Oracle returns the correct info for SQL_DESC_PRECISION as 19, 22 and 29 ), I have to implement a workaroudn only for Oracle ODBC driver to SQLDescribeCol and took at the column size for timestamp columns to figure out precision
if ( column type is SQL_TYPE_TIMESTAMP and precision == 19 )
precision = precision < 20 ? 0 : columnsize - 20
Obviously column size 20 does not make sense because that would be just a decimal point after the seconds part and fractions.
The Oracle driver has a bug with SQLColAttribute SQL_DESC_PRECISION since it returns the correct precision for DATE columns but not for TIMESTAMP columns that were introduced with 9i.
Thanks for the workaround.