Computer Science - 9210 OxfordAQA

Relational Databases

Bayani Gaba-gaba

Write a customer's address on every order they place and you have created a problem you will not notice for months. Then they move. Now some orders carry the old address and some carry the new one, both are in the same file, and nothing in the data says which is correct. The information has not been lost. It has been duplicated, and duplication is how data becomes untrustworthy.

This lesson explains what a database is, what makes one relational, and the five terms the specification examines: table, record, field, primary key and foreign key. Then it explains the reason the whole design exists. Splitting data across linked tables so that each fact is stored exactly once is what makes redundancy and inconsistency avoidable, and being able to say precisely how it does that is worth more marks than being able to name the parts.

Manufura

  1. Explain the concept of a database. Explain the concept of a relational database. Understand the following important database concepts.
  2. table
  3. record
  4. field
  5. primary key
  6. foreign key.
  7. Understand that the use of a relational database facilitates the elimination of data inconsistency and data redundancy.

Taswirar tunani

An zana wannan batu don ka ga yadda ra'ayoyi ke hadewa.

Bude taswirar tunani a cikin manhaja

Takardar Darasi

A database is an organised collection of data, stored so that it persists, and structured so that it can be searched, added to, changed and retrieved reliably. The word doing the work in that sentence is organised. A folder full of notes is data and is not a database, because nothing about it says what a record is, which pieces belong together, or how to find one.

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Nazarin Darasi

Barka da kammala darasi akan Relational Databases. Yanzu da kuka bincika mahimman raayoyi da raayoyi, lokaci yayi da zaku gwada ilimin ku. Wannan sashe yana ba da ayyuka iri-iri Tambayoyin da aka tsara don ƙarfafa fahimtar ku da kuma taimaka muku auna fahimtar ku game da kayan.

Za ka gamu da haɗe-haɗen nau'ikan tambayoyi, ciki har da tambayoyin zaɓi da yawa, tambayoyin gajeren amsa, da tambayoyin rubutu. Kowace tambaya an ƙirƙira ta da kyau don auna fannoni daban-daban na iliminka da ƙwarewar tunani mai zurfi.

Yi wannan ɓangaren na kimantawa a matsayin wata dama don ƙarfafa fahimtarka kan batun kuma don gano duk wani yanki da kake buƙatar ƙarin karatu. Kada ka yanke ƙauna da duk wani ƙalubale da ka fuskanta; maimakon haka, ka kallesu a matsayin damar haɓaka da ingantawa.

  1. What is a record in a relational database? A. One column of a table B. All the data about one individual item, held as one row C. The name of a table D. A link between two tables Answer: B
  2. What is a primary key? A. A field whose value uniquely identifies each record in a table B. The first field listed in a table C. A field that holds a value from another table D. The password used to open the database Answer: A
  3. A Booking table contains a field MemberID which holds values from the Member table's primary key. What is MemberID in the Booking table? A. A primary key B. A record C. A foreign key D. A table Answer: C
  4. What is data redundancy? A. Data that is no longer needed and can be deleted B. Storing the same piece of data more than once C. Data that has been encrypted D. A field with no value in it Answer: B
  5. Why can data inconsistency not occur if a fact is stored exactly once? A. Because a single copy cannot disagree with anything B. Because single copies are always encrypted C. Because a single copy takes up less space D. Because tables cannot be linked Answer: A

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Yi aikin wadannan tambayoyi a cikin manhaja

Yi Aikin Tambayoyin Gwaji

Kana son yin aikin tambayoyin gwaji kan Relational Databases? Sauke manhajar Green Bridge CBT don samun tambayoyin gwaji da cikakkun jarrabawa akan wannan batu.

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