Hi,
Standard tables are managed system-internally by a table index. New rows are either attached to the table or added at certain positions. The table key or the index identify individual rows.
Sorted tables are managed by a table index (like standard tables). The entries are listed in ascending order according to table key.
Hashed tables are managed by a hash algorithm. There is no table index. The entries are not ordered in the memory. The position of a row is calculated by specifying a key using a hash function.
The generic table types define a generic table type that can only be
used for typing formal parameters and field symbols:
ANY TABLE includes all table types.
INDEX TABLE includes all standard tables and sorted tables.
Hash Algorithm:
A hash function is any well-defined procedure or mathematical function for turning some kind of data into a relatively small integer, that may serve as an index into an array. The values returned by a hash function are called hash values, hash codes, hash sums, or simply hashes.
Hash functions are mostly used to speed up table lookup or data comparison tasks --- such as finding items in a database, detecting duplicated or similar records in a large file, finding similar stretches in DNA sequences, and so on.
Hash functions are related to (and often confused with) checksums, check digits, fingerprints, randomizing functions, error correcting codes, and cryptographic hash functions. Although these concepts overlap to some extent, each has its own uses and requirements. The HashKeeper database maintained by the National Drug Intelligence Center, for instance, is more aptly described as a catalog of file fingerprints than of hash values.
For more details:
[Hash Function|http://en.wikipedia.org/wiki/Hash_function]
Regards
Kannaiah
Bluesky
