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SAP Sybase SQL Anywhere 16.0 » UltraLite - C and C++ Programming » Application development » UltraLite C++ application development » Data creation and modification using SQL statements » Data modification using INSERT, UPDATE and DELETE


Deleting a row in a table

UltraLite indicates query parameters using the ? character. For any INSERT, UPDATE, or DELETE statement, each ? is referenced according to its ordinal position in the prepared statement. For example, the first ? is referred to as parameter 1, and the second as parameter 2.


There are no prerequisites for this task.

  1. Declare a ULPreparedStatement using the following code:

    ULPreparedStatement * prepStmt;
  2. Prepare a SQL statement for execution.

    The following code prepares a DELETE statement for execution:

    prepStmt = conn->PrepareStatement("DELETE FROM MyTable(MyColumn1) VALUES (?)");
  3. Check for errors when preparing the statement.

    For example, the following code is useful when checking for SQL syntax errors:

    if( prepStmt == NULL ) {
        const ULError * ulerr;
        ulerr = conn->GetLastError();
        // write code to handle the error
  4. Set values to replace ? characters in the prepared statement.

    The following code sets ? characters to 7 while error checking. For example, an error is caught when the parameter ordinal is out of range for the number of parameters in the prepared statement.

    ul_s_long value_to_delete = 7;
    if( !prepStmt->SetParameterInt(1, value_to_delete) ) {
        const ULError * ulerr;
        ulerr = conn->GetLastError();
        // write code to handle the error.
  5. Execute the prepared statement, deleting the data from the database.

    The following code checks for errors that could occur after executing the statement. For example, an error is returned if you try deleting a row that has a foreign key referenced to it.

    bool success;
    success = prepStmt->ExecuteStatement();
    if( !success ) {
        const ULError * ulerr;
        ulerr = conn->GetLastError();
        // write code to handle the error
    } else {
        // Use the following line if you are interested in the number of rows deleted ...
        ul_u_long rowsDeleted = prepStmt->GetRowsAffectedCount();
  6. Clean up the prepared statement resources.

    The following code releases the resources used by the prepared statement object. This object should no longer be accessed after the Close method is called.

  7. Commit the data to the database.

    The following code saves the data to the database and prevents data loss. The data from step 5 is lost if the device application terminates unexpectedly before the application completes a commit call.



Row entries from MyTable are deleted where the MyColumn value in the table is equal to 7.