2.2.15

Structured Query Language

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Structured Query Language

A database is a structured collection of data. Structured query language (SQL) is a language used to query this data.

SQL

SQL

  • SQL is a language that can tell databases what to do.
  • SQL can be used for selecting, inserting, updating, and deleting data.
  • For GCSE you only need to know how to select (search for) data.
Select statements

Select statements

  • A SELECT statement searches for and returns data. E.g:
    • SELECT * FROM table_name;
  • The * character tells the database to return all fields.
  • The * character can be replaced by specific fields. E.g:
    • SELECT name FROM users;
Where clause

Where clause

  • Sometimes we don't want to return data for all records.
  • We can filter the data using a where clause as follows:
    • SELECT * FROM users WHERE ID=3;
  • The above line would only return a user's data where they have an ID of 3.
Wildcards

Wildcards

  • Sometimes we don't know the exact value we want to use in a where clause.
  • We can use wildcards to find records which match some sort of pattern.
  • We can use the % symbol to represent anything. For example, if we want to find any names starting with 'Ba' then we could query:
    • SELECT name FROM users WHERE name LIKE "Ba%";
Jump to other topics
1

Computer Systems

1.1

Systems Architecture

1.1.1Fetch-Execute Cycle1.1.2Common CPU Components & Their Function1.1.3Von Neumann Architecture1.1.4Factors Affecting CPU Performance1.1.5Embedded Systems1.1.6Exam-Style Questions - Von Neumann Architecture1.1.7Diagnostic Misconceptions - Embedded vs General
1.2

Memory & Storage

1.2.1Types of Memory1.2.2Flash Memory1.2.3Properties of Flash Memory1.2.4Running Out of Memory1.2.5Virtual Memory1.2.6Units of Capacity1.2.7Calculating Capacity Requirements1.2.8Solid State Storage1.2.9Properties of Solid State Media1.2.10Magnetic Storage1.2.11Properties of Magnetic Media1.2.12Examples of Magnetic Storage1.2.13Optical Storage1.2.14Properties of Optical Media1.2.15Examples of Optical Storage1.2.16Types of Optical Disk1.2.17Number Bases1.2.18Converting Number Bases1.2.19Hexadecimal1.2.20Using Hexadecimal1.2.21Converting Denary & Hexadecimal1.2.22Binary Addition1.2.23Binary Shifts1.2.24Representing Text1.2.25ASCII & Unicode1.2.26Representing Images1.2.27Converting Binary & Images1.2.28Representing Sound1.2.29Data Compression1.2.30Grade 9 - Storage1.2.31Exam-Style Questions - Primary Memory1.2.32Exam-Style Questions - Storage1.2.33Exam-Style Questions - Data Conversions1.2.34Diagnostic Misconceptions - RAM vs ROM1.2.35Diagnostic Misconceptions - Bits, Nibbles & Bytes1.2.36Diagnostic Misconceptions - Bits Required to Store1.2.37End of Topic Test - Computer Systems1.2.38End of Topic Test - Representation
1.3

Computer Networks, Connections & Protocols

1.3.1Benefit of Networks1.3.2Types of Networks1.3.3Network Performance1.3.4Networks: How Do Packets Get Routed?1.3.5Client-Server Model1.3.6Pros & Cons of Client-Server Model1.3.7Peer-to-Peer Model1.3.8Pros & Cons of Peer-to-Peer Model1.3.9Network Hardware1.3.10Transmission Media1.3.11What is the Internet?1.3.12URLs1.3.13DNS & Web Hosting1.3.14The Cloud1.3.15Pros & Cons of the Cloud1.3.16Star & Mesh Network Topologies1.3.17WiFi1.3.18WiFi Frequency & Channels1.3.19WiFi Encryption1.3.20IP Addresses1.3.21MAC Addresses1.3.22Network Protocols1.3.23Transmission Protocols1.3.24Application Protocols1.3.25Layers1.3.26Advantages of Layering1.3.27Exam-Style Questions - Networking Models1.3.28Exam-Style Questions - Network Protocols1.3.29Diagnostic Misconceptions - LAN vs WAN
1.4

Network Security

1.4.1Forms of Attack1.4.2Penetration Testing1.4.3Malware1.4.4How Malware Spreads1.4.5Social Engineering1.4.6Phishing1.4.7Cracking Passwords1.4.8Denial of Service Attacks1.4.9Data Interception1.4.10Methods of Data Interception1.4.11SQL Injection1.4.12Network Administration1.4.13Network Forensics1.4.14Protecting Against Malware1.4.15Firewalls1.4.16User Access Levels1.4.17Passwords1.4.18Encryption1.4.19End of Topic Test - Networks
1.5

Systems Software

1.5.1System Software1.5.2Utility Software1.5.3Operating Systems1.5.4User Interfaces1.5.5Memory & Process Management1.5.6File Management1.5.7Device Management1.5.8User Management1.5.9Encryption Software1.5.10Defragmentation Software1.5.11Data Compression Software1.5.12Backup Software
1.6

Ethical, Legal, Cultural & Environmental Concern

1.6.1Open Source Software1.6.2Proprietary Software1.6.3Licensing Issues1.6.4Ethical Issues - The Digital Divide1.6.5Ethical Issues - Net Neutrality1.6.6Ethical Issues - Working Conditions1.6.7Ethical Issues - Censorship1.6.8Exam-Style Questions - Ethical Issues1.6.9Data Protection Act 19981.6.10Computer Misuse Act (1990)1.6.11Copyright Designs & Patents Act (1988)1.6.12Creative Commons Licensing1.6.13Freedom of Information Act (2000)1.6.14Cultural Issues1.6.15Environmental Issues1.6.16Online Activity Tracking & The Internet of Things1.6.17Stakeholders1.6.18Other Impacts of Digital Technology on Society1.6.19End of Topic Test - Software & Issues1.6.20Diagnostic Misconceptions - Open Source
2

Computational Thinking, Algorithms & Programming

2.1

Algorithms

2.1.1Computational Thinking - Abstraction2.1.2Computational Thinking - Decomposition2.1.3Algorithmic Thinking2.1.4Pseudocode2.1.5Flowchart Diagrams2.1.6Interpreting Algorithms2.1.7Correcting Algorithms2.1.8Completing Algorithms2.1.9Search Algorithms2.1.10Binary Search2.1.11Linear Search2.1.12Overview of Sort Algorithms2.1.13Bubble Sort2.1.14Merge Sort2.1.15Insertion Sort2.1.16Exam-Style Questions - Sorting Algorithms
2.2

Programming Fundamentals

2.2.1Variable Declaration & Assignment2.2.2Input & Output2.2.3Program Flow - Sequence2.2.4Program Flow - Selection2.2.5Program Flow - Iteration2.2.6Arithmetic Operators2.2.7Relational Operators2.2.8Boolean Operators2.2.9Data Types2.2.10Casting2.2.11Arrays2.2.12Strings2.2.13File Handling2.2.14Structuring Data - Records2.2.15Structured Query Language2.2.16Random Number Generation2.2.17End of Topic Test - Programming2.2.18Exam-Style Questions - Translation2.2.19Diagnostic Misconceptions - Comparison Operators2.2.20Diagnostic Misconceptions - = & ==2.2.21Diagnostic Misconceptions - Types of Data2.2.22Diagnostic Misconceptions - Last Line of Code2.2.23Diagnostic Misconceptions - Array Index
2.3

Producing Robust Programs

2.3.1Defensive Design2.3.2Validation & Sanitisation2.3.3Authentication & Contingencies2.3.4Maintainability2.3.5Purpose of Testing2.3.6Types of Testing2.3.7Test Plans2.3.8Types of Errors2.3.9End of Topic Test - Programming2.3.10Exam-Style Questions - Testing
2.4

Boolean Logic

2.4.1Binary Systems2.4.2Logic Circuits2.4.3Boolean Logic2.4.4Boolean Operators2.4.5Grade 9 - Logic
2.5

Programming Languages & IDEs

2.5.1High-Level vs Low-Level Languages2.5.2Translation - Compliers & Interpreter2.5.3Translation - Assemblers2.5.4Integrated Development Environments2.5.5Exam-Style Questions - Translation

Practice questions on Structured Query Language

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    What does the * wildcard mean in SQL?Multiple choice
  2. 2
    In which order, are the three key SQL commands written to execute a query?Multiple choice
  3. 3
    What is the purpose of the SELECT key term in an SQL command?Multiple choice
  4. 4
    What is the purpose of the FROM key term in an SQL command? Multiple choice
  5. 5
    What is the purpose of the WHERE key term in an SQL command?Multiple choice
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Structuring Data - Records

Random Number Generation