Removing Rows From a Table Using the SQL DELETE Statement

    Procedure

  1. Formulate a SQL DELETE string for removing rows of data from a table.

  2. Call the createStatement() method of the Session object. Pass the SQL DELETE string as an argument.
  3. If the SQL DELETE string contains parameter markers, call the Statement methods to set the parameter values.
  4. Run the DELETE statement by calling the executeUpdate() method of the Statement object.

  5. Check the result of the executeUpdate() method to verify that the correct number of rows have been removed from the table.

  6. Set different parameter values and rerun the DELETE statement by repeating steps 3 to 5.

  7. Close the Statement object.

Deleting large number of rows

When removing a large number of rows from a table, TIBCO recommends to remove batches of rows versus the entire set of rows.

To delete a large number of rows from a table, design a SQL DELETE statement as follows:

  1. Design a range query which is bounded on both ends to select a subset of rows to be removed from the table.

  2. Avoid unbounded range queries to reduce the number of rows scanned. For example, use a WHERE clause similar to the following:

    WHERE key >= 0 AND key <=1000

    WHERE key BETWEEN 0 AND 1000

  3. Use parameters in the range query which results in a subset of rows being removed each time executeUpdate() is invoked. For example,

    WHERE key BETWEEN ? AND ?

  4. Design the WHERE clause so that an index is used for finding the rows and prevent full table scans.

  5. Set the statement property TIBDG_STATEMENT_PROPERTY_DOUBLE_UPDATE_TIMEOUT so the executeUpdate requests do not timeout.

    The SQL LIMIT clause is not part of the syntax for SQL DELETE.