Database Fundamentals Database Fundamentals SQL Joins 1 SQL – WHERE Logical conditions often used to filter results: Use these to test values and combine tests with AND/OR as required 2 Condition Description = Equals Not equal < Less than > Greater than = Greater than or equal to LIKE Partial matches (string comparison) Use ‘%’ […]
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DB Fundamentals DB Security You have the power! 1 1 DB Security Security Discretionary Access Control Views & Stored Procedures Backup and Recovery Integrity Encryption Duplication/Raid 2 DB Security Discretionary Access Control (DAC) 3 DB Security – Access Control Access control defines what a user can and cannot do Discretionary Access Control (DAC) Involves GRANT
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Database Fundamentals Aggregate Queries SUM, Avg, MIN, MAX … Example database – Employees & Departments FirstName Surname Dept Office Salary City Mary Brown Administration 10 45 London Charles White Production 20 36 Toulouse Gus Green Administration 20 40 Oxford Jackson Neri Distribution 16 45 Dover Charles Brown Planning 14 80 London Laurence Chen Planning 7
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Database Fundamentals SQL – Functions – CAST CAST is used to convert an expression of one data type to another Syntax CAST ( expression AS data_type [ ( length ) ] ) Arguments expression Any valid expression. data_type Is the target data type (INT, VARCHAR, BIT etc) length Is an optional integer that specifies the length of
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DB Fundamentals DB Fundamentals Triggers NOTE: Defining triggers differs dramatically between DBMS DML Triggers A trigger is a special kind of a stored procedure that executes in response to certain action on a table (or in a DB) The action could be On insertion of a new record On deletion of existing record On Updating
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THE UNIVERSITY OF SUSSEX INFORMATICS BSc FINAL YEAR EXAMINATION 2021 MComp THIRD YEAR EXAMINATION 2021 January 2021 (A1) Introduction to Computer Security Candidates should answer TWO questions out of THREE. If all three questions are attempted only the first two answers will be marked. Each question is worth 50 marks. Write your answers on A4
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DB Fundamentals Stored Procedures Stored Queries called on demand! Stored Procedures Stored Procedures (SPs) are pre-written SQL queries stored by the DBMS They are similar to Views in that they are called when required They (technically) do not store data Unlike views they may contain INSERT, UPDATE, DELETE, SELECT queries or any combination of these!
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Database Fundamentals Database Fundamentals SQL Introduction – Data Manipulation Language 1 SQL Commands Overview – Data Manipulation Key Data Manipulation SQL commands: INSERT INTO – Creates new tuple(s) in a table in the database DELETE FROM – Permanently removes tuple(s) UPDATE – Modifies existing tuple(s) in a table in the database SELECT – Retrieves one
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PowerPoint Presentation Database Fundamentals Introduction to Databases Database Overview What is a database? A handful of tables containing data that are used to retrieve information A collection of potentially useful data that models real-world or conceptual objects and their relationships Objects/Entities like People, items, Purchases, Students etc Relationships like Jim purchased a book Conceptual like
Database Fundamentals Database Fundamentals Normalisation Concepts Normalisation Database designs can be generated by decomposing “Mega” relational schemas into smaller schemas Based on knowledge of the attributes and relationships between them called Functional Dependencies (FDs) These smaller relations satisfy some normal form in that they contain fewer anomalies and that there is no loss of information