a database key facilitating direct access to data on a storage device. See key and direct access.
Hashing
An indexing technique where an algorithm is used to calculate the location of a row or record, requiring a full key look-up and an exact match, including upper and lower case characters, spaces, and punctuation.
Having
An SQL statement clause that allows additional criteria to be applied to an SQL statement after the WHERE and GROUP BY clauses have been processed. The HAVING clause is generally used to apply criteria to an aggregation as in “SUM(ORDERS.TOTAL)>10”.
HDC
Hashed Data Cache - This is an internal technique that Omnidex uses for internal optimization. It is an in memory hash table.
In OdxSQL Explain Plans, HDC can show up when reviewing optimization of a query.
High cardinality
(1) High table cardinality indicates a large number of records in a table, a Sales Fact table for example.
(2) High column cadinality indicates many possible unique values in a column. For example, names, addresses, account balances, product inventories, etc. See cardinality.
Hints
A method of forcing the Omnidex Optimizer to use a particular retrieval method, in a star schema database environment, for example.
Host
A generic term for any device that allows communication from an outside source.
Hybrid DR
Hybrid Detail Record; a variation of a multi-domain child, providing the ability to index a child table as a DR domain or in an SI domain. See DR domain and SI domain.