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Data warehousingIn addition to designing and implementing HCL OneDB™ dimensional databases, you can use tools to create data warehouse applications and optimize your data warehouse queries.
Dimensional databasesThe HCL OneDB™ Data Warehouse Guide provides information to help you design, implement, and manage dimensional databases, and describes the tools that you can use to create data warehouses and optimize your data warehouse queries.
Performance tuning dimensional databasesThis section describes how to tune the performance of your queries and to understand data distribution statistics.
Query execution plansWhen a SELECT statement or other DML operation is submitted to the database server, the query execution optimizer designs a query execution plan. The query execution optimizer is often referenced as the query optimizer.

Query execution plans

When a SELECT statement or other DML operation is submitted to the database server, the query execution optimizer designs a query execution plan. The query execution optimizer is often referenced as the query optimizer.

To design a query execution plan, and estimate the costs of candidate query plans, the query optimizer considers a wide range of information including:

Specifications that identify the database objects, predicates, filters, joins, and other operations in the SQL syntax that defines the query operation
System catalog information about indexes and constraints on the tables, views, and columns that are referenced or implied in the query
Data distribution statistics for the tables and indexes, or for their fragments, that are referenced or implied in the query
Optimizer directives that are specified inline or as external optimizer directives that favor or avoid subsets of the potential query plans
Information in the database server environment or in the session environment that affects the query execution optimizer

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