COMPUTER SCIENCE AND ENGINEERING
SQL
|
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
|
|
|
Evaluation algebra
|
|
|
Evaluation plan
|
|
|
Evaluation primitive
|
|
|
Evaluation engine
|
Detailed explanation-1: -Explanation: A relational algebra operation annotated with instructions on how to evaluate it is called Evaluation primitive. The evaluation primitive is the basis for evaluation of queries. Explanation: A sequence of primitive operations that can be used to evaluate a query are called as Query evaluation plan.
Detailed explanation-2: -1. Select Operation: The select operation selects tuples that satisfy a given predicate. It is denoted by sigma ().
Detailed explanation-3: -Five basic operations in relational algebra: Selection, Projection, Cartesian product, Union, and Set Difference.
Detailed explanation-4: -When a user executes any query, for generating the internal form of the query, the parser in the system checks the syntax of the query, verifies the name of the relation in the database, the tuple, and finally the required attribute value. The parser creates a tree of the query, known as ‘parse-tree.
Detailed explanation-5: -➢ Four main Phases: decomposition, optimization, code generation and execution. Activity of choosing an efficient execution strategy for processing query. ➢ As there are many equivalent transformations of same high-level query, aim of QO is to choose one that minimizes resource usage.