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AdministeringIn addition to administering the database server, you can tune performance, replicate data, and archive data.
System administrationThese topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL OneDB™ database servers.
Performance GuideThe HCL OneDB™ Performance Guide describes how to configure and operate your HCL OneDB™ database server to improve overall system throughput and to improve the performance of SQL queries.
Queries and the query optimizerThese topics describe query plans, explain how the database server manages query optimization, and discuss factors that you can use to influence the query plan. These topics also describe performance considerations for SPL routines, the UDR cache, and triggers.
The query planThe query optimizer evaluates the different ways in which a query might be performed and determines the best way to select the requested data. During this evaluation, the optimizer formulates a query plan to fetch the data rows that are required to process a query.
Sample query plan reportsThe topics in this section describe sample query plans that you might want to display when analyzing the performance of different kinds of queries.
Query plans for collection-derived tablesA collection-derived table is a special method that the database server uses to process a query on a collection. To use a collection-derived table, a query must contain the TABLE keyword in the FROM clause of an SQL statement.

Query plans for collection-derived tables

A collection-derived table is a special method that the database server uses to process a query on a collection. To use a collection-derived table, a query must contain the TABLE keyword in the FROM clause of an SQL statement.

For more information about how to use collection-derived tables in an SQL statement, see the HCL OneDB™ Guide to SQL: Syntax.

Although the database does not actually create a table for the collection, it processes the data as if it were a table. Collection-derived tables allow developers to use fewer cursors and host variables to access a collection, in some cases.

These SQL statements create a collection column called children:

CREATE ROW TYPE person(name CHAR(255), id INT);
CREATE TABLE parents(name CHAR(255),
id INT,
children LIST(person NOT NULL));

The following query creates a collection-derived table for the children column and treats the elements of this collection as rows in a table:

SELECT name, id 
FROM TABLE(MUTLISET(SELECT children 
FROM parents 
WHERE parents.id
= 1001)) c_table(name, id);

Alternatively, you can specify a collection-derived table in the FROM clause, as shown in this example:

SELECT name, id 
FROM (SELECT children 
FROM parents 
WHERE parents.id
= 1001) c_table(name, id);