Databases

• What is 1NF?


  1st normal form:

  • Repeating groups are removed

  • The table of each attribute contains only atomic values
• What is 2NF?


  2nd normal form:

  • Every non-primary key attribute is fully dependent on the primary key

  • 1NF
• What is 3NF?


  3rd normal form:

  • A non-primary key attribute is dependent on the primary key

  • 2NF
• What does ACID stand for?

  Atomicity, Consistency, Isolation, Durability
• What is the concatenated primary key?

  When more than one field is added together to form a unique primary key.
• What does ERM stand for?

  Entity relationship modelling - creating tables with relationships between the entities to normalise a data set.
• What is a flat file database?

  All data is contained in one table with no normalisation.
• What is the foreign key?

  A primary key of one table that appears as an attribute in another table and acts to provide a logical relationship between the two tables
• What is indexing?


  The process of creating a database index, which is a data structure improving the speed of data retrieval.
• What is normal form?

  A way of structuring the data in a relational database according to formal rules.
• What is normalisation?


  The process of arriving at third normal form for a database from a flat file.
• What is the primary key?

  A field that uniquely identifies a record in a table.
• What is record locking?


  A technique of preventing simultaneous access to data in a database, to prevent inconsistent results.
• What is redundancy?


  A field that is repeated in more than one table.
• What is referential integrity?

  A measure of the consistency of the data in a database.
• What is a relational database?


  Multiple tables with relationships between them.
• What is the secondary key?

  A field used to speed up searching and sorting.
• What is SQL?


  Structured Query Language - a language to return, define and manipulate records in a database.
• What is transaction processing?

  Information processing that is divided into individual, indivisible operations called transactions.
• What is a one-to-many relationship?

  A One-to-Many relationship between two entities indicates that one record in Entity A corresponds to multiple records in Entity B but one record in Entity B has only one associated record in Entity A.
• What is durability?


  Once a change has taken place in a database, the change must not be lost.

  This is achieved by the whole transaction being immediately written to permanent secondary storage.
• What is a composite key?


  When more than one field is combined to create a unique primary key for a table.
• What is consistency?


  Transactions will go from one consistent state to another (outcome should not be different before and after committing).
• What is the purpose of the INSERT structure in SQL?

  It is used to add a new record into an existing table.INSERT INTO Student_details VALUES (‘Amanda Jones’, 15/10/1980, ‘F’)
• What is the purpose of the DROP structure in SQL?

  To delete a table from a database.
• What is the purpose of the LIKE structure in SQL?

  To enable to the use of wildcards in WHERE statements.WHERE surname LIKE 'S%
• What is OCR and what is an example of its usecase?

  Optical Character Recognition.

  It can be used for a traffic speed camera to capture the number plates of speeding drivers.
• What is the purpose of the FROM structure in SQL?

  To define which tables will be used.
• What is data integrity?

  Data integrity is the maintenance and consistency of data in a data store. Data can become inconsistent if changes are applied to fields in one table and not other tables.
• What is a method of data exchange between systems?

  JSON. XML came first but now many applications use JSON.
• What is OMR and what is an example of its usecase?

  Optical Marking Recognition.

  It can be used for lottery tickets and multiple choice exam papers being scanned and the data input into a database.
• What is an advantage of traditional paper based forms to capture data?

  There is no need for technology and an internet connection to collect the data.
• What is the purpose of the DELETE structure in SQL?

  To delete records from a database table.
• What is EDI and what is an example of its usecase?

  Electronic Data Interchange.

  An example of its use would be a school wanting to automatically connect its information systems to the exam board so that candidate information and results are downloaded quickly on results day.
• What is the purpose of the WHERE structure in SQL?

  To define criteria upon which records will be returned. E.g. WHERE surname = 'Smith'.
• What is isolation?


  A transaction must be performed in such a way that other processes can't have access to the data. This is performed by record locking.