JDBC ResultSet Objects
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Questions and Answers

What is the initial position of the cursor in a ResultSet object?

  • Randomly positioned within the ResultSet
  • At the last row of data
  • At the first row of data
  • Before the first row of data (correct)

    • Which property of a default ResultSet object restricts how it can be iterated?

  • It can be updated with new data
  • It can only move forward through the rows (correct)
  • It can display changes made by others
  • It can only move backward through the rows

    • How can you retrieve data from a ResultSet more efficiently?

  • Using random access
  • Using a mix of column names and indices
  • Using column index numbers (correct)
  • Using column names only

    • What happens if a getter method is called with a column name that has duplicates in the ResultSet?

    <p>The value of the first matching column is returned</p> Signup and view all the answers

    What is the purpose of the 'TYPE_SCROLL_INSENSITIVE' in the ResultSet creation?

    <p>To ensure the ResultSet does not show changes made by others</p> Signup and view all the answers

    Why should result set columns within each row be read in left-to-right order?

    <p>To ensure compatibility with all JDBC drivers</p> Signup and view all the answers

    What type of values does a JDBC driver return when using getter methods on a ResultSet?

    <p>Java types specified in the getter method</p> Signup and view all the answers

    What is a key characteristic of an updatable ResultSet?

    <p>It allows for modifications to the data</p> Signup and view all the answers

    What is the purpose of the SQL AS clause in the context of using column names?

    <p>To ensure column names have unique references.</p> Signup and view all the answers

    How can an updater method be used in the context of a ResultSet?

    <p>To update values in the current row.</p> Signup and view all the answers

    What functionality does an updatable ResultSet provide that enhances data manipulation?

    <p>Provides a staging area for inserting rows.</p> Signup and view all the answers

    What happens to a ResultSet object when the Statement object associated with it is closed?

    <p>The ResultSet is automatically closed.</p> Signup and view all the answers

    In the provided code fragment, which method is used to update the data source after changing a value in a ResultSet?

    <p>updateRow()</p> Signup and view all the answers

    What is the primary role of ResultSetMetaData in relation to ResultSet objects?

    <p>To provide information about the columns of a ResultSet.</p> Signup and view all the answers

    When updating a column in the current row, what is the first method called to position the cursor in the provided code example?

    <p>absolute()</p> Signup and view all the answers

    When using an updatable ResultSet, which of the following is necessary before inserting a new row?

    <p>The cursor should be moved to the insert row.</p> Signup and view all the answers

    What is the primary purpose of the ResultSet.moveToInsertRow method?

    <p>To navigate to a special row for constructing a new row.</p> Signup and view all the answers

    After inserting a row with ResultSet.insertRow, what should you do next?

    <p>Move the cursor to a row other than the insert row.</p> Signup and view all the answers

    Which method is called to update a column in the insert row before inserting it into the ResultSet?

    <p>ResultSet.updateString</p> Signup and view all the answers

    What can happen if another part of your application uses the same ResultSet while the cursor is still pointing to the insert row?

    <p>Unexpected results can occur in the ResultSet.</p> Signup and view all the answers

    What does ResultSet.CONCUR_UPDATABLE indicate?

    <p>The ResultSet can be updated by calling insert or update methods.</p> Signup and view all the answers

    What is the default concurrency level for a ResultSet object?

    <p>CONCUR_READ_ONLY</p> Signup and view all the answers

    Which method would you call to check if a specified ResultSet type is supported by the JDBC driver?

    <p>DatabaseMetaData.supportsResultSetType</p> Signup and view all the answers

    Which of the following options can be specified when creating a ResultSet to allow cursor movement both forwards and backwards?

    <p>TYPE_SCROLL_SENSITIVE</p> Signup and view all the answers

    What happens to ResultSet objects when the Connection.commit method is called?

    <p>They are closed if they are non-holdable.</p> Signup and view all the answers

    When using getter methods with a string as an identifier, how are multiple columns with the same name handled?

    <p>The first matching column's value is returned.</p> Signup and view all the answers

    Which method must be called after modifying a value in a ResultSet to persist changes to the underlying database?

    <p>ResultSet.updateRow</p> Signup and view all the answers

    Which JDBC driver feature may not be supported by all databases regarding ResultSet handling?

    <p>HOLD_CURSORS_OVER_COMMIT</p> Signup and view all the answers

    Which method is recommended to retrieve a VARCHAR column value from a ResultSet?

    <p>getString</p> Signup and view all the answers

    What is a key characteristic of ResultSet objects' default scroll sensitivity?

    <p>They can only be scrolled forward.</p> Signup and view all the answers

    When using case-insensitive column names with getter methods, what should be ensured?

    <p>Column names must be unique in the query result.</p> Signup and view all the answers

    When a ResultSet is created and the cursor is positioned before the first row, which method is used to move the cursor to the first row?

    <p>ResultSet.next</p> Signup and view all the answers

    In the context of ResultSet property holdability, what does HOLD_CURSORS_OVER_COMMIT allow?

    <p>ResultSet objects to not close on commit.</p> Signup and view all the answers

    To increase the likelihood of portability across different JDBC drivers, what is recommended when retrieving columns from a ResultSet?

    <p>Read columns in left-to-right order.</p> Signup and view all the answers

    What might be a limitation when using getString to retrieve numeric types from a ResultSet?

    <p>It converts the numeric value back to string requiring additional conversion.</p> Signup and view all the answers

    Which of the following statements is true regarding the cursor in a ResultSet object?

    <p>The cursor is a pointer that starts positioned before the first row.</p> Signup and view all the answers

    What distinguishes a TYPE_FORWARD_ONLY ResultSet from other ResultSet types?

    <p>It is limited to moving the cursor only in a forward direction.</p> Signup and view all the answers

    What is the purpose of the ResultSet.next method?

    <p>To advance the cursor to the next row and return its status.</p> Signup and view all the answers

    Which statement correctly describes the capabilities of the ResultSet interface?

    <p>It includes methods for both retrieving and manipulating query results.</p> Signup and view all the answers

    Which type of ResultSet cannot reflect changes made to the underlying database after it has been created?

    <p>TYPE_SCROLL_INSENSITIVE</p> Signup and view all the answers

    How is the sensitivity of a ResultSet defined?

    <p>By the ResultSet type and how it handles data changes.</p> Signup and view all the answers

    What is a characteristic of a PreparedStatement in relation to a ResultSet?

    <p>It can create ResultSet objects through execution of SQL queries.</p> Signup and view all the answers

    What happens if ResultSet.next returns false?

    <p>There are no more rows available for processing in the ResultSet.</p> Signup and view all the answers

    What type of SQL statements can be included in the batch that utilizes the executeBatch method?

    <p>INSERT, UPDATE, DELETE statements</p> Signup and view all the answers

    What behavior must be disabled before beginning a batch update to allow for correct error handling?

    <p>Auto-commit mode</p> Signup and view all the answers

    What method is used to clear the list of commands associated with a Statement object?

    <p>clearBatch</p> Signup and view all the answers

    If a batch contains a SELECT statement, what kind of exception is thrown?

    <p>BatchUpdateException</p> Signup and view all the answers

    What does the Statement.executeBatch method return if all commands are executed successfully?

    <p>An array of affected rows</p> Signup and view all the answers

    What will happen if the Connection.commit method is not called after a batch update?

    <p>The updates will not be permanent.</p> Signup and view all the answers

    Which of the following correctly identifies a potential limitation when using ResultSet for updates?

    <p>Not all JDBC drivers support inserting new rows with ResultSet.</p> Signup and view all the answers

    Which command is correctly associated with adding a new SQL command to the batch?

    <p>addBatch</p> Signup and view all the answers

    What must be done to the Connection object to enable auto-commit mode after completing a batch update?

    <p>Manually set auto-commit to true.</p> Signup and view all the answers

    What structure stores the update counts produced by successful commands in a batch?

    <p>UpdateCount array</p> Signup and view all the answers

    How are SQL commands executed in relation to their order in the batch?

    <p>In the order they were added to the batch.</p> Signup and view all the answers

    What kind of exception contains an array of update counts similar to what the executeBatch method yields?

    <p>BatchUpdateException</p> Signup and view all the answers

    Which method is called on a ResultSet to begin inserting a new row?

    <p>insertRow</p> Signup and view all the answers

    Study Notes

    ResultSet Objects in JDBC

    • ResultSet objects store the results of database queries.
    • Initialized: Cursor positioned before the first row.
    • Iteration: next() method moves cursor to the next row. Returns false when no more rows exist, usable in a while loop.
    • Default: Non-updatable, forward-only cursor. Only iterates through the result once in a forward order.
    • Scrollable and Updatable: Create updatable result sets with a specific statement.
    Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
ResultSet rs = stmt.executeQuery("SELECT a, b FROM TABLE2");
    • This creates a scrollable ResultSet (not affected by changes from other sources) and updatable.
    • Retrieving Values: Getter methods (getBoolean, getLong, etc.) retrieve column values.
      • Use column index (starting at 1) or name. Column index is more efficient.
      • Read columns in left-to-right order and only once per column for best practice.
      • Column names are case-insensitive. Pick the first matching column.
      • Use column names when they're explicitly in the SQL query; use column numbers for unnamed columns.
    • JDBC Data Type Mapping: ResultSet getter methods translate SQL types to Java types. JDBC spec (table) describes allowed mappings.
    • Updater Methods (JDBC 2.0+):
    • Modify existing rows.
    rs.absolute(5); // move cursor to the 5th row
rs.updateString("NAME", "AINSWORTH"); // update NAME to AINSWORTH
rs.updateRow();  // Update the database row
    • Add new rows:
    rs.moveToInsertRow(); // Move to the special insert row
rs.updateString(1, "AINSWORTH"); // Set the first column in the insert row 
rs.updateInt(2,35);
rs.updateBoolean(3, true);
rs.insertRow();  //add to the database
rs.moveToCurrentRow();  // Go back to regular data rows
    • ResultSet Closure: Automatically closed when parent Statement closes, re-executed, or used for subsequent results in a sequence.
    • Metadata: ResultSet.getMetaData() returns ResultSetMetaData which gives information about the result set, like the number of columns and column types.

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    Description

    Explore the functionality of ResultSet objects in JDBC. Understand how to initialize, iterate, and retrieve values from a database query. This quiz covers updatable and scrollable ResultSet concepts as well.

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