1.3.2 Databases

“Allows the user to specify information about multiple tables and the relationship between those tables”

“A database that allows the user to specify data attributes (columns, databases etc.) for only one table at a time, storing those attributes independently”

“A field that uniquely identifies a record in a table”

“The linking field in the foreign table formed when a relationship is made. The FK becomes by default the PK of the new table.”

“When more than one field is added together to form a unique primary key for a table.”

“A key field which can be used to access a table in a different way”

Entity Relationship Modelling: “The process of producing a data model for describing the data or information aspects of a business domain or its process requirements, in an abstract way that lends itself to ultimately being implemented in a data such as a relation database.”

“The process of arranging data in tables and setting their relationships to move them through normal forms”

“The process of creating a database index, which is a data structure that improves the speed of data retrieval operations on a dataset table at the cost of additional writes and storage space to maintain the index data structure.”

“A table with no normalisation. All data and all fields in one table”

First Normal Form: “A relationship with repeating groups removed. That is a relation in which the intersection of each tuple and attribute contains one and only one value.”

Second Normal Form: “A relation that is in 1NF and every non-primary key attribute is fully dependant on the primary key. That is, all the incomplete dependencies have been removed”

Third Normal Form: “A relation that is in 1NF and 2NF, and in which no non-primary key attribute is transitively dependent on the primary key. That is, all non-key elements are fully dependent on the primary key”

“A way of structuring the data in a relational database according to formal rules, in order to avoid problems of efficiency and security in accessing and maintain the data.”

Structured Query Language: “The language and syntax used to write and run database queries”

“A measure of the consistency of the data in a database. It is violated when the relation to which a foreign key refers to no longer exists.”

“Information processing that is divided into individual, indivisible operations, called transactions. Each transaction must succeed or fail as a complete unit, it can never be only partially complete.”

Atomicity, Consistency, Isolation, Durability: “A set of properties that guarantee that database transactions are processed reliably. In the context of databases, a single logical operation on the data is called a transaction.”

“A technique of preventing simultaneous access to data in a database, to prevent inconsistent results. The classic example is demonstrated by two bank clerks attempting to update the same bank account for two different transactions.”

“Redundancy occurs in database systems which have a field that is repeated in two or more tables For instance, when customer data is duplicated and attached with each product bought, then redundancy of data is a known source of inconsistency since customer might appear with different values for given attributes.”