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Updated the embedded sample program to reflect latest class functions. Added a generic HandleError() function as part of the sample program to show a simple way of getting error messages fro database calls

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Insert/Query/Delete examples shown in the sample


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@27021 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
George Tasker
2004-04-30 11:11:40 +00:00
parent 66c033b4a6
commit e31a990025
1 changed files with 151 additions and 75 deletions
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226
docs/latex/wx/tdb.tex
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@@ -557,7 +557,7 @@ can specify anywhere from one column up to all columns in the table.
\begin{verbatim}
table->SetColDefs(0, "FIRST_NAME", DB_DATA_TYPE_VARCHAR, FirstName,
SQL_C_CHAR, sizeof(name), true, true);
SQL_C_CHAR, sizeof(FirstName), true, true);
table->SetColDefs(1, "LAST_NAME", DB_DATA_TYPE_VARCHAR, LastName,
SQL_C_CHAR, sizeof(LastName), true, true);
\end{verbatim}
@@ -920,136 +920,207 @@ report the bugs/problems you have encountered in the latter case.
Simplest example of establishing/opening a connection to an ODBC datasource,
binding variables to the columns for read/write usage, opening an
existing table in the datasource, setting the query parameters
existing table in the datasource, inserting a record, setting query parameters
(where/orderBy/from), querying the datasource, reading each row of the
result set, then cleaning up.
result set, deleting a record, releasing the connection, then cleaning up.
NOTE: Not all error trapping is shown here, to reduce the size of the
code and to make it more easily readable.
NOTE: Very basic error handling is shown here, to reduce the size of the
code and to make it more easily readable. The HandleError() function uses the wxDbLogExtendedErrorMsg() function for retrieving database error messages.
\begin{verbatim}
wxDbConnectInf *DbConnectInf = NULL;
// ----------------------------------------------------------------------------
// HEADERS
// ----------------------------------------------------------------------------
#include "wx/log.h" // #included to enable output of messages only
#include "wx/dbtable.h"
wxDb *db = NULL; // The database connection
wxDbTable *table = NULL; // The data table to access
// ----------------------------------------------------------------------------
// FUNCTION USED FOR HANDLING/DISPLAYING ERRORS
// ----------------------------------------------------------------------------
// Very generic error handling function.
// If a connection to the database is passed in, then we retrieve all the
// database errors for the connection and add them to the displayed message
int HandleError(wxString errmsg, wxDb *pDb=NULL)
{
// Retrieve all the error message for the errors that occurred
wxString allErrors;
if (!pDb == NULL)
// Get the database errors and append them to the error message
allErrors = wxDbLogExtendedErrorMsg(errmsg.c_str(), pDb, 0, 0);
else
allErrors = errmsg;
wxChar FirstName[50+1]; // buffer for data from column "FIRST_NAME"
wxChar LastName[50+1]; // buffer for data from column "LAST_NAME"
// Do whatever you wish with the error message here
// wxLogDebug() is called inside wxDbLogExtendedErrorMsg() so this
// console program will show the errors in the console window,
// but these lines will show the errors in RELEASE builds also
wxFprintf(stderr, wxT("\n%s\n"), allErrors.c_str());
fflush(stderr);
bool errorOccured = false;
return 1;
}
const wxChar tableName[] = "CONTACTS";
const UWORD numTableColumns = 2; // Number of bound columns
FirstName[0] = 0;
LastName[0] = 0;
// ----------------------------------------------------------------------------
// entry point
// ----------------------------------------------------------------------------
int main(int argc, char **argv)
{
wxDbConnectInf *DbConnectInf = NULL; // DB connection information
DbConnectInf = new wxDbConnectInf(NULL,"MyDSN","MyUserName", "MyPassword");
wxDb *db = NULL; // Database connection
wxDbTable *table = NULL; // Data table to access
const wxChar tableName[] = wxT("USERS"); // Name of database table
const UWORD numTableColumns = 2; // Number table columns
wxChar FirstName[50+1]; // column data: "FIRST_NAME"
wxChar LastName[50+1]; // column data: "LAST_NAME"
wxString msg; // Used for display messages
// -----------------------------------------------------------------------
// DEFINE THE CONNECTION HANDLE FOR THE DATABASE
// -----------------------------------------------------------------------
DbConnectInf = new wxDbConnectInf(NULL,
wxT("CONTACTS-SqlServer"),
wxT("sa"),
wxT("abk"));
// Error checking....
if (!DbConnectInf || !DbConnectInf->GetHenv())
{
wxMessageBox("Unable to allocate an ODBC environment handle",
"DB CONNECTION ERROR", wxOK | wxICON_EXCLAMATION);
return;
}
return HandleError(wxT("DB ENV ERROR: Cannot allocate ODBC env handle"));
}
// Get a database connection from the cached connections
// -----------------------------------------------------------------------
// GET A DATABASE CONNECTION
// -----------------------------------------------------------------------
db = wxDbGetConnection(DbConnectInf);
// Create the table connection
table = new wxDbTable(db, tableName, numTableColumns, "",
!wxDB_QUERY_ONLY, "");
if (!db)
{
return HandleError(wxT("CONNECTION ERROR - Cannot get DB connection"));
}
// -----------------------------------------------------------------------
// DEFINE THE TABLE, AND THE COLUMNS THAT WILL BE ACCESSED
// -----------------------------------------------------------------------
table = new wxDbTable(db, tableName, numTableColumns, wxT(""),
!wxDB_QUERY_ONLY, wxT(""));
//
// Bind the columns that you wish to retrieve. Note that there must be
// 'numTableColumns' calls to SetColDefs(), to match the wxDbTable definition
// 'numTableColumns' calls to SetColDefs(), to match the wxDbTable def
//
// Not all columns need to be bound, only columns whose values are to be
// returned back to the client.
//
table->SetColDefs(0, "FIRST_NAME", DB_DATA_TYPE_VARCHAR, FirstName,
SQL_C_CHAR, sizeof(name), true, true);
table->SetColDefs(1, "LAST_NAME", DB_DATA_TYPE_VARCHAR, LastName,
SQL_C_CHAR, sizeof(LastName), true, true);
table->SetColDefs(0, wxT("FIRST_NAME"), DB_DATA_TYPE_VARCHAR, FirstName,
SQL_C_CHAR, sizeof(FirstName), true, true);
table->SetColDefs(1, wxT("LAST_NAME"), DB_DATA_TYPE_VARCHAR, LastName,
SQL_C_CHAR, sizeof(LastName), true, true);
// Open the table for access
table->Open();
// -----------------------------------------------------------------------
// CREATE (or RECREATE) THE TABLE IN THE DATABASE
// -----------------------------------------------------------------------
if (!table->CreateTable(true)) //NOTE: No CommitTrans is required
{
return HandleError(wxT("TABLE CREATION ERROR: "), table->GetDb());
}
// -----------------------------------------------------------------------
// OPEN THE TABLE FOR ACCESS
// -----------------------------------------------------------------------
if (!table->Open())
{
return HandleError(wxT("TABLE OPEN ERROR: "), table->GetDb());
}
// -----------------------------------------------------------------------
// INSERT A NEW ROW INTO THE TABLE
// -----------------------------------------------------------------------
wxStrcpy(FirstName, wxT("JULIAN"));
wxStrcpy(LastName, wxT("SMART"));
if (!table->Insert())
{
return HandleError(wxT("INSERTION ERROR: "), table->GetDb());
}
// Must commit the insert to write the data to the DB
table->GetDb()->CommitTrans();
// -----------------------------------------------------------------------
// RETRIEVE ROWS FROM THE TABLE BASED ON SUPPLIED CRITERIA
// -----------------------------------------------------------------------
// Set the WHERE clause to limit the result set to return
// all rows that have a value of 'GEORGE' in the FIRST_NAME
// all rows that have a value of 'JULIAN' in the FIRST_NAME
// column of the table.
table->SetWhereClause("FIRST_NAME = 'GEORGE'");
table->SetWhereClause(wxT("FIRST_NAME = 'JULIAN'"));
// Result set will be sorted in ascending alphabetical
// order on the data in the 'LAST_NAME' column of each row
table->SetOrderByClause("LAST_NAME");
table->SetOrderByClause(wxT("LAST_NAME"));
// No other tables (joins) are used for this query
table->SetFromClause("");
table->SetFromClause(wxT(""));
// Instruct the datasource to perform a query based on the
// criteria specified above in the where/orderBy/from clauses.
if (!table->Query())
{
wxMessageBox("Error on Query()","ERROR!",
wxOK | wxICON_EXCLAMATION);
errorOccured = true;
return HandleError(wxT("QUERY ERROR: "), table->GetDb());
}
wxString msg;
// Start and continue reading every record in the table
// displaying info about each record read.
// Loop through all rows matching the query criteria until
// there are no more records to read
while (table->GetNext())
{
msg.Printf("Row #%lu -- First Name : %s Last Name is %s",
table->GetRowNum(), FirstName, LastName);
wxMessageBox(msg, "Data", wxOK | wxICON_INFORMATION, NULL);
msg.Printf(wxT("Row #%lu -- First Name : %s Last Name is %s"),
table->GetRowNum(), FirstName, LastName);
// Code to display 'msg' here
wxLogMessage(wxT("\n%s\n"), msg.c_str());
}
// -----------------------------------------------------------------------
// DELETE A ROW FROM THE TABLE
// -----------------------------------------------------------------------
// Select the row which has FIRST_NAME of 'JULIAN' and LAST_NAME
// of 'SMART', then delete the retrieved row
//
// Select the row which has FIRST_NAME of 'GEORGE' and LAST_NAME
// of 'TASKER', then delete the retrieved row
//
table->SetWhereClause("FIRST_NAME = 'GEORGE' and "LAST_NAME = 'TASKER'");
if (table->Query())
if (!table->DeleteWhere(wxT("FIRST_NAME = 'JULIAN' and LAST_NAME = 'SMART'")))
{
table->Delete();
// Must commit the deletion
table->GetDb()->CommitTrans();
return HandleError(wxT("DELETION ERROR: "), table->GetDb());
}
//
// Insert a new row into the table
//
wxStrcpy(FirstName, "JULIAN");
wxStrcpy(LastName, "SMART");
table->Insert();
// Must commit the insert
// Must commit the deletion to the database
table->GetDb()->CommitTrans();
// -----------------------------------------------------------------------
// TAKE CARE OF THE ODBC CLASS INSTANCES THAT WERE BEING USED
// -----------------------------------------------------------------------
// If the wxDbTable instance was successfully created
// then delete it as we are done with it now.
if (table)
{
wxDelete(table);
}
wxDELETE(table);
// If we have a valid wxDb instance, then free the connection
// Free the cached connection
// (meaning release it back in to the cache of datasource
// connections) for the next time a call to wxDbGetConnection()
// is made.
if (db)
{
wxDbFreeConnection(db);
db = NULL;
}
wxDbFreeConnection(db);
db = NULL;
// -----------------------------------------------------------------------
// CLEANUP BEFORE EXITING APP
// -----------------------------------------------------------------------
// The program is now ending, so we need to close
// any cached connections that are still being
// maintained.
@@ -1057,8 +1128,13 @@ wxDbCloseConnections();
// Release the environment handle that was created
// for use with the ODBC datasource connections
wxDelete(DbConnectInf);
wxDELETE(DbConnectInf);
wxUnusedVar(argc); // Here just to prevent compiler warnings
wxUnusedVar(argv); // Here just to prevent compiler warnings
return 0;
}
\end{verbatim}
\subsection{A selection of SQL commands}\label{sqlcommands}