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Articles by Bhanu Priya
Page 68 of 106
Explain the difference between physical and logical databases
Logical Database Design has a low-level description of entities that are defined and how they are related to each other and what kind of data is to be stored. This model determines if all the requirements of the business have been gathered.Physical Database Design deals with how the data will be stored in the database using suitable DBMS and this design is generally created by database administrators and developers.DifferencesThe major differences between logical database design and physical database design are as follows −Logical Database DesignPhysical Database DesignThat describes the data without regard to how they will be physically implemented in ...
Read MoreExplain the factors influencing physical database design
Physical database designing is used for good performance while the process of structuring data in the storage.Factors influencing physical database designLet us see the important factors that influence physical database design −Transactions and queriesIt is important to understand what kind of transactions and queries will be run and what use will the database serve.Following information about the queries should be needed −Files that will query access.Selection conditions to be specified for the query.Type of selection conditions to be used in query whether equality, range, or inequality.Join conditions to be used in the query.Need for linking tables for query optimization.Following information ...
Read MoreWhat are integrity constraints over the relation in DBMS?
For any stored data if we want to preserve the consistency and correctness, a relational DBMS typically imposes one or more data integrity constraints. These constraints restrict the data values which can be inserted into the database or created by a database update.Data Integrity ConstraintsThere are different types of data integrity constraints that are commonly found in relational databases, including the following −Required data − Some columns in a database contain a valid data value in each row; they are not allowed to contain NULL values. In the sample database, every order has an associated customer who placed the order. ...
Read MoreWhat is B-tree and explain the reasons for using it (DBMS)?
Let us first try to understand why we are using B-tree. Then, we will get a clarity on the definition of B-tree.Reasons for using B-treeThe reasons for using B-tree are as follows −When searching tables on disc, the cost of accessing the disk is high but it doesn’t bother about the amount of data transferred. So our aim is to minimize disc access.We know that we cannot improve the height of trees. So, we wish to make the height of the tree as small as possible.The solution for this is to use a B-tree, it has more branches and thus ...
Read MoreState the advantages and disadvantages of collision resolution strategies
The advantages and disadvantages of some of the collision resolution techniques are explained below −Separate Chaining hashingSeparate chaining is a hashing technique in which there is a list to handle collisions. So there are many elements at the same position and they are in a list. The sequences are maintained in a linked list.The advantages of separate chaining hashing are as follows −Separate chaining technique is not sensitive to the size of the table.The idea and the implementation are simple.The disadvantages of separate chaining hashing are as follows −Keys are not evenly distributed in separate chaining.Separate chaining can lead to ...
Read MoreWhat are collision avoidance techniques(DBMS)?
Collision is a problem that occurs when two keys applied on a hash table map to the same location in the hash table.There are two techniques that are used to avoid collision they are −Linear probing.Chaining.Let us discuss each technique in detail.Linear probingLinear probing is a strategy for resolving collisions. In this the new key is placed in the closest following empty cell.Here the elements are stored wherever the hash function maps into a hash table, if that cell is filled then the next consecutive location is searched to store that value. Here generally we use arrays.Step 1 − Let ...
Read MoreWhat are different hashing methods in DBMS?
Hashed file organisation is also called a direct file organisation.In this method, for storing the records a hash function is calculated, which provides the address of the block to store the record. Any type of mathematical function can be used as a hash function. It can be simple or complex.Hash function is applied to columns or attributes to get the block address. The records are stored randomly. So, it is also known as Direct or Random file organization.If the generated hash function is on the column which is considered as key, then the column can be called as hash key ...
Read MoreExplain the importance of centralized databases
Different organizations have struggled with their management information systems and their membership databases. The main struggle here is the lack of centralized information. Too often, assurance and non-profits keep separate databases for membership, events, sales, and other processes. When at all feasible, these databases should be combined into a single, centralized database.Advantages of centralized database over other databasesThe advantages of centralized database over other databases are explained below −Data integrity − In a centralized database the data integrity is maximized and data redundancy is minimized, as the single storing place of all the data also implies that a given set ...
Read MoreWhat is a distributed database?
A distributed database is the one where all the storage devices are not attached to a common CPU (central processing unit). It may be distributed over a network of interconnected computers, or it may be stored in multiple computers located in the same physical location.Distributed Database Management SystemA distributed database management system (DDBMS) manages the database as in if it is stored in the same computer.The DDBMS synchronizes all the data in a periodical manner and in situations when multiple users are accessing the same data and ensures that updation and deletion performed on the data at one location shall ...
Read MoreWhat is the primary index in DBMS?
In the primary index there is a one-to-one relationship between the entries in the index table and records in the main table. Primary index is used on a primary key.Types of Primary IndexPrimary index are of two types, which are as follows −Dense Primary IndexIn a dense primary index an index record appears for every search key value in the main table that means each and every record in the main table has an entry in the index.ExampleGiven below is an example of dense primary index −A pointer stores the address of a record.Non-Dense / Sparse Primary indexAn index record ...
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