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What are the services of Query Management?
Query management services are the set of possibilities that handle the exchange between the query production, the implementation of the query on the database, and the return of the result set to the desktop. These services have a full impact on customer cooperation with the database.
There are various services of Query management which are as follows −
Content simplification − These techniques try to safeguard the user from the complexities of the data and the query language before some definite queries are formulated. This includes limiting the user’s view to subsets of the tables and columns, predefined join rules (including columns, types, and path preferences), and standard filters.
Content simplification metadata is generally definite to the front-end tool instead of generally available service. The simplification rules are usually hidden in the frontend tool’s metadata repository.
Query retargeting and multipass SQL − The query retargeting service parses the incoming query, looks up the elements in the metadata to see where they exist, and then redirects the query or its components as appropriate. This involves simple divert, heterogeneous joins, and set functions including union and minus.
This simple-sounding function is really what creates it possible to host independent fact tables on independent hardware platforms. It allows us to query data from two fact tables, like manufacturing costs and customer sales, on two different servers, and seamlessly integrate the results into a customer contribution report.
Aggregate awareness − Aggregate awareness is a certain case of query retargeting where the service identifies that a query can be fulfilled by an available aggregate table instead of summing up detailed data on the fly. For instance, if someone questions for sales by month from the daily table, the service cause redefine the query to run opposite to the monthly fact table.
The aggregate navigator is the element that supports this aggregate awareness. In the method that indexes are selected by the database application, the aggregate navigator facility automatically selects aggregates.
The best aggregate navigators are separate from the end-user tools and support the aggregate navigation benefit for some users sending SQL to the DBMS. An aggregate navigator that is embedded in the end-user tool is isolated to that specific tool and creates a problem for the DBA who must support multiple tools in a complex environment.
The best aggregate navigator supports statistics on all incoming SQL and not only documents on the custom levels of current aggregates but suggests more aggregates that should be developed by the DBA.
Date awareness − The date awareness service enables the user to question items such as current year-to-date and previous year-to-date sales without having to figure out the definite date ranges. This generally contains maintaining attributes in the period’s dimension table to recognize the applicable dates.
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