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=item get_record_hash 

the same

=back 

=head2 Writing the data

=over 4

Basically like above, but do not specify the ID, leave it to DB_File::DB_Database. 
The ID will be sequent numbers.
On success they return true -- the record ID. Index file is automatical updated, if needed.

=item set_record

the same, recommand to use for updating data 

=item set_record_hash

the same, recommand to use for updating data 

=item update_record_hash

the same 

=item delete_record 

the same 

=item append_record 

As parameters, takes the list of values of the fields. It append the record to the file. 
Unspecified fields (if you pass less than you should) are set to undef/empty. 
ID will be returned. 

=item append_record_hash 

Unspecified fields (if you pass less than you should) are set to undef/empty. 
ID will be returned. 

=back 

Examples: 

    $table->append_record("Caroline", "20", "sister");
    $table->append_record_hash('jimmy', "age" => 25,
                                        "msg" => 'Nothing is easy!');

=head2 Using Index

=over 4

Index file is stored in DB_File BTREE. Once created, all index files will be automatically 
opened when open the database file, and updated automatically when writing the database file.

=item create_index 

Create index file for one field. Default permits of the index file is 0640. 'name' is the index 
tag name, 'key' is the formula for indexing. For example:

  'key' => 'Age'            # index by the age, from young to old
  'key' => '-Age'           # index by the age, from old to young
  'key' => '-Age(3)+Name'   # index by the age(up to 999),then name; from old to young,then from A to Z
  'key' => '-Age(3)+-Name'  # index by the age(up to 999),then name; from old to young,then from Z to A

'Age(3)' is similar to 'substr(Age,0,3)', only the length of the last field name appeared in 
the 'key' can be ommited. '+-' CAN'T be subsituded by '-'.

  # Index File name will be dbexample_indexA 
  print $table->create_index( 'name'   => 'indexA' ,
                              'key'    => 'Age' ,       # '-Age' means reverse sort,
                              'permits'=> 0640 );    

=item recreate_index

Recreate the index file. Parameter is the index name(s). 

=item drop_index

Delete the index file. Parameter is the index name(s). 

  # delete Index indexA 
  print $table->drop_index('indexA');  

=back

=head2 Select records

=over 4

Select matched records, using index will speed up the searching.

=item prepare_select

As parameters, pass a hash as parameters. Almost each value is a hash reference. Eg: 
  # find people aged form 10 to 25, select the first 10 people. their 'msg' must content 'hi'
  $table->prepare_select( "seek"  => {'index'=> 'indexA',
                                      'from' => 10,
                                      'to'   => 25},
                          "where" => {'msg'=> 'hi'},
                          "top"   => 10);

If no "seek" specified(do not use index), it will search from the first record to the last(or up to the record numbers you needed)."top" means select the first ? records. You may use "cut" instead, "cut" => [2,6] means select from the secord matched ...

for "seek", "from" is needed, "to" can be omitted(till the last). 

To fetch the selected record. Use get_record, get_record_nf, get_record_hash, leave the ID undef. 

=back

Examples of selecting record:

    use DB_File::DB_Database;
    my $table = new DB_File::DB_Database "dbexample" or die DB_File::DB_Database->errstr;
    my $table = new XBase "names.dbf" or die XBase->errstr;
    # find people aged form 10 to 25, select the first 10 people. their 'msg' must content 'hi'
    $table->prepare_select( "seek"  => {'index'=> 'indexA',
                                        'from' => 10,
                                        'to'   => 25},