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Multilevel Indexing
in Database is created when a primary index does not fit in memory. In this type of indexing method, you can reduce the number of disk accesses to short any record and kept on a disk as a sequential file and create a sparse base on that file.
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secondary Index
can be generated by a field which has a unique value for each record, and it should be a candidate key. It is also known as a non-clustering index. This two-level database indexing technique is used to reduce the mapping size of the first level.
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B-tree index
is the widely used data structures for tree based indexing in DBMS. It is a multilevel format of tree based indexing in DBMS technique which has balanced binary search trees. All leaf nodes of the B tree signify actual data pointers.
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Query processing
is a process of translating a user query into an executable form. It helps to retrieve the results from a database. In query processing, it converts the high level query into a low-level query for the database
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Disk Accesses
time to process a data request and retrieve the required data from the storage device.
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selection operator (𝜎)
is a unary operator in relational algebra. We use it to select the relation's records or rows that satisfy its condition(s).
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Projection Operation (represented by π)
belongs to relational algebra, which displays the specific column of a table mentioned in the query. It is a unary operation that returns its argument relation, with certain attributes left out.
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join operation
combines rows from two or more relations based on a related column between them, creating a result set with columns from both relations.
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Right Outer Join
Returns all rows from the right table
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Left Outer Join
Returns all rows from the left table
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Using Full Join
Returns all rows from both table
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Projection operation
focuses on selecting specific attributes from a single relation
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Join operation
is used to combine data from multiple relations based on a common column