0
Queries of a database can be fast or slow. Depends on a lot of things. The size of the table, the amount of data you are requesting from the query, etc. One of the ways a dba can help query optimization, is by "updating statistics" on a table. Statistics of a table allows the query to find the most efficient way to gather the data from the table.
Wiki User
∙ 15y ago
Add your answer:
Earn +20 pts
Why DBA understand query optimization?
he is the main person for the data administration for the relational database management systems. therefore, he needs to understand the query plan and be able to suggest the suitable query plan that would satisfy the query.
What is the main four phases of query processing in dbms?
Query processing can be divided into four main phases: decomposition, optimization, code generation, and execution.
How you Explain heuristics-based optimization in a distributed database system?
In Heuristic-based Optimization, the query execution is refined based on heuristic rules for reordering the individual operations.
What is the goal of query optimization Why it is important?
The goal of query optimization is to reduce the system resources required to fulfill a query, and ultimately provide the user with the correct result set faster. Query optimization is important for at least a few reasons. First, it provides the user with faster results, which makes the application seem faster to the user. Secondly, it allows the system to service more queries in the same amount of time, because each request takes less time than unoptimized queries. Thirdly, query optimization ultimately reduces the amount of wear on the hardware (e.g. disk drives), and allows the server to run more efficiently (e.g. lower power consumption, less memory usage).
What is heuristic optimization?
Where the 'query tree' or 'algebra tree' is transformed using a set of predefined rules that will improve the queries performance. Performing the selections as early as possible to reduce load. It is a form of Query Processing.
Why would you want to override automatic query optimization?
Sometimes, the query designer may know information that can be overlooked by the query optimizer. Often, in the course of testing queries, one may find that it is actually faster not to use a certain index or to use a different index. When this is the case, database management systems such as Oracle include a facility to override the query optimizer, called query hints.
What has the author A Illarramendi written?
A. Illarramendi has written: 'Query optimization for KBMSs' -- subject(s): Telos (Computer program knowledge), Database management
Why global query optimization is difficult in distributed dbms?
1:parallel execution 2: Additional communication cost 3: Transparency and replication
Why database system support data manipulation using a declarative query languages?
Declarative query languages allow users to specify what data they want without specifying how to retrieve it. This abstraction simplifies the querying process and allows for optimization by the database system to determine the most efficient way to execute the query. It also enhances portability and adaptability by separating the query logic from the database structure.
Can write query within the query?
Yes, you can have a query inside a query. That is known as a sub-query.
A query that prompts for input whenever it is run is a run-time query?
A query that prompts for input whenever it is run is a Paremeter Query
What is post query and pre query?
pre query
