Using the IN modifier in the WHERE clause in Java

Drawer PDF 417 in Java Using the IN modifier in the WHERE clause

try { String query = new String ("SELECT " + "FirstName, LastName, Street, City, State, ZipCode, Sales " + " FROM Customers " + " WHERE Sales NOT IN (20000, 30000, 40000) " ); DataRequest = DatabasecreateStatement(); Results = DataRequestexecuteQuery (query);

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DisplayResults (Results); DataRequestclose(); }

Metadata is data that describes data, which you learned about in 6 Metadata is returned with the ResultSet object and can be extracted from the ResultSet object by creating a ResultSetMetaData Techniques for doing this are described in the next several sections of this chapter Metadata can be used in a J2ME application for various purposes, such as to display the column name of a column and determine the data type of a column The most commonly used metadata are Column name Column number Column data type

Listing 11-39 contains the DownRow() method that illustrates how to determine the number of columns in the ResultSet The getMetaData() method is called to extract metadata from the ResultSet The getMetaData() method returns a ResultSetMetaData object, which is called metadata in this example The ResultSetMetaData object contains several methods that are used to copy specific metadata from the ResultSet In this example, the getColumnCount() method is called to retrieve the number of columns contained in the result set, which is then assigned to the NumberOfColumns variable and printed on the screen using the println() method (This doesn t work with all drivers) The DownRow() method in Listing 11-39 can replace the DownRow() method in the Model B program and be used in any version of the Model B program presented in this chapter Of course, the DownRow() method must be modified to copy and display data contained in the ResultSet, as shown previously in this chapter

Listing 11-39 Determining the number of columns in a ResultSet private void DownRow ( ResultSet DisplayResults )throws SQLException { ResultSetMetaData metadata = DisplayResultsgetMetaData (); int NumberOfColumns; String printrow; NumberOfColumns = metadatagetColumnCount (); Systemoutprintln("Number Of Columns: " + NumberOfColumns); }

Listing 11-40 illustrates how to determine the data type of a column You ll notice that this technique is very similar to the technique for retrieving the number of columns in the ResultSet described in the previous section In this example the getColumnTypeName() method is called to copy the data type from column nine of the result set to the ColumnType object Any valid column number in the ResultSet can be passed to the getColumnTypeName() method You can use the data type returned by the getColumnTypeName() method to determine the proper getXXX() method to use to copy data from the ResultSet The type is returned as the native type, not the SQL type

Listing 11-40 Determining the data type of columns in a ResultSet private void DownRow ( ResultSet DisplayResults ) throws SQLException { ResultSetMetaData metadata = DisplayResultsgetMetaData (); String ColumnType = new String(); String printrow; ColumnType = metadatagetColumnTypeName ( 9 ); Systemoutprintln("Column Type: " + ColumnType ); }

Retrieving the column name from the metadata uses a process similar to copying the data type of a column from the metadata In the example in Listing 11-41, the getColumnLabel() method is used to copy the column name from a specific column and assign the column name to the String object ColumnName The number of the column in the ResultSet is passed to the getColumnLabel() method

Listing 11-41 Determining the names of columns in a ResultSet private void DownRow ( ResultSet DisplayResults ) throws SQLException { ResultSetMetaData metadata = DisplayResultsgetMetaData (); String ColumnName = new String(); String printrow; ColumnName = metadatagetColumnLabel (9) ; Systemoutprintln("Column Name: " + ColumnName); }

The column size, also referred to as the column width, is called the display size and represents the number of characters needed to display the maximum value that might be stored in the column You retrieve the display size by using the getColumnDisplaySize( ) method, as illustrated in Listing 11-42 This listing is similar to the others in the metadata sections The getColumnDisplaySize( ) is called and passed the number of the column whose

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