Explain ACID properties with examples.

-

 ACID and Relational Databases

Four crucial properties define relational database transactions: atomicity, consistency, isolation, and durability-typically referred to as ACID. 

  • Atomicity defines all the elements that make up a complete database transaction or none.
  • Consistency defines the rules for maintaining data points in a correct state after a transaction. Isolation keeps the effect of a transaction invisible to others until it is committed, to avoid confusion. 
  • Durability ensures that data changes become permanent once the transaction is committed.

A Relational Database Example

Here is a simple example of two tables that a small firm may use to process product orders. The first table is a customer information table, which means that each entry contains a customer's name, address, shipping and payment information, phone number, and other contact information. Each piece of information (each attribute) is in its column, and each row is assigned a unique ID (a key) in the database. Each entry in the second table-a customer order table-includes the ID of the customer who made the purchase, the product ordered, the quantity, the size, and color are chosen, and so on-but not the client's name or contact information.

The only thing these two tables have in common is the ID column (the key). However, because of the shared field, the relational database may establish a link between the two tables. When the company's order processing application submits an order to the database, the database can go to the customer order table, pull the correct product order information, and use the customer ID from that table to look up the customer's billing and shipping information in the customer info table. The database system can then fetch the proper product, the client will receive the order on schedule, and the firm will be compensated.



Comments

Post a Comment

Popular posts from this blog

Suppose that a data warehouse for Big-University consists of the following four dimensions: student, course, semester, and instructor, and two measures count and avg_grade. When at the lowest conceptual level (e.g., for a given student, course, semester, and instructor combination), the avg_grade measure stores the actual course grade of the student. At higher conceptual levels, avg_grade stores the average grade for the given combination. a) Draw a snowflake schema diagram for the data warehouse. b) Starting with the base cuboid [student, course, semester, instructor], what specific OLAP operations (e.g., roll-up from semester to year) should one perform in order to list the average grade of CS courses for each BigUniversity student. c) If each dimension has five levels (including all), such as “student < major < status < university < all”, how many cuboids will this cube contain (including the base and apex cuboids)?

-
Image
a) A Snowflake Shema is shown in figure below: b) The specific OLAP operations to be performed: 1. Roll-up on course from course_id to department. 2. Roll-up on a student from student_id to university. 3. Dice on course, student with department ="CS" and university = "biguniversity" 4. Drill-down on a student from the university to student_name. c) N = 4 dimensions The cube will contain 54 = 625 cuboids.
Read more

Suppose that a data warehouse consists of the four dimensions; date, spectator, location, and game, and the two measures, count and charge, where charge is the fee that a spectator pays when watching a game on a given date. Spectators may be students, adults, or seniors, with each category having its own charge rate. a) Draw a star schema diagram for the data b) Starting with the base cuboid [date; spectator; location; game], what specific OLAP operations should perform in order to list the total charge paid by student spectators at GM Place in 2004?

-
Image
  b) The specific OLAP operations to be performed are: 1. Roll-up on date from date id to year. 2. Roll-up on spectator from spectator id to status. 3. Roll-up on location from location id to location name. 4. Roll-up on the game from game id to all. 5. Dice with status= “students”, location name= “GM Place”, and year=2004
Read more

Explain network topology .Explain tis types with its advantages and disadvantges.

-
Network topology Network topology refers to how the nodes and links in a network are arranged. A network node is a device that can send, receive, store, or forward data. A network link connects nodes and may be either cabled or wireless links. Understanding topology types provides the basis for building a successful network. There are a number of topologies but the most common are bus, ring, star, and mesh: A bus network topology is when every network node is directly connected to a main cable. In a ring topology, nodes are connected in a loop, so each device has exactly two neighbors. Adjacent pairs are connected directly; non-adjacent pairs are connected indirectly through multiple nodes. In a star network topology, all nodes are connected to a single, central hub and each node is indirectly connected through that hub.  A mesh topology is defined by overlapping connections between nodes. You can create a full mesh topology, where every node in the network is connected to every other
Read more