KS3 Computer Science

11-14 Years Old

48 modules covering EVERY Computer Science topic needed for KS3 level.

GCSE Computer Science

14-16 Years Old

45 modules covering EVERY Computer Science topic needed for GCSE level.

A-Level Computer Science

16-18 Years Old

66 modules covering EVERY Computer Science topic needed for A-Level.

GCSE SQL (14-16 years)

  • An editable PowerPoint lesson presentation
  • Editable revision handouts
  • A glossary which covers the key terminologies of the module
  • Topic mindmaps for visualising the key concepts
  • Printable flashcards to help students engage active recall and confidence-based repetition
  • A quiz with accompanying answer key to test knowledge and understanding of the module

A-Level SQL (16-18 years)

  • An editable PowerPoint lesson presentation
  • Editable revision handouts
  • A glossary which covers the key terminologies of the module
  • Topic mindmaps for visualising the key concepts
  • Printable flashcards to help students engage active recall and confidence-based repetition
  • A quiz with accompanying answer key to test knowledge and understanding of the module

What is SQL

On the most fundamental level, SQL is a programming language intended for overseeing and questioning social information bases, which were designed during the 1970s and advocated by Oracle. Simply put, social information bases sort out information into lines and segments (like Excel!); in the event that you need to truly know a great deal, gain proficiency with Codd’s Twelve Rules that granularly characterise a social data set administration framework. Truly, some questionnaires may solicit your feelings from those guidelines eventually.

SQL permits you to adjust an information base’s record structures, recover data, and create new relations. The language goes about as the establishment for an assortment of innovation capacities for instance, a framework for monitoring usernames and passwords. That is the reason endless businesses need engineers to know SQL; in the event that you truly try to dazzle a forthcoming manager with your insight, you could even examine how business SQL IDEs assist you with finishing certain errands (Squirrel!), however as a rule, essentially showing a serious extent of capability is sufficient.

Definition of SQL

SQL (Structured Query Language) is a generic programming language used to track the basis of social knowledge and to execute various information procedures. Initially developed during the 1970s, SQL is commonly used by knowledge base administrators, as well as by engineers writing material for data integration and data examiners hoping to set up and run explanatory inquiries.

SQL code is isolated into four fundamental allocations:

Questions are conducted using the universal and familiar explanation of SELECT, which is further categorised into sentences, like SELECT, FROM, WHERE and ORDER BY.

In order to supervise relations and record systems, Knowledge Description Language (DDL) is used. Establish, Modify, TRUNCATE and DROP integrate instances of DDL articulations.

To allocate and refuse data set privileges and consents, Information Management Language (DCL) is used. GRANT and REVOKE are the foundational proclamations.

Why Do We Learn SQL?

SQL is a truly important aptitude to learn and ace and is additionally instinctive and simple to utilise. It’s utilised all over the place and for an assortment of purposes including: account, music, web-based media, information examination, and so forth Consequently, the individuals who are talented in SQL are consistently sought after. A greater part of organisations utilises huge, social information bases and are continually searching for individuals who have what it takes to use SQL.

How Quickly We Learn SQL?

Learning SQL is a touch simpler on the off chance that you know about other programming dialects, explicitly C#, JavaScript, or PHP. Regardless of your aptitude level, however, the classes and courses we will examine here are learn-at-your-own-pace, so there’s a horrible response to “how rapidly would we be able to learn?” Even after you ace the essentials, it’s consistently a smart thought to keep getting the hang of all that you can about SQL if simply because it’ll assist you with acing other information base advances, for example, NoSQL. (No, the adapting never stops. Welcome to tech!)

Most ideal Ways to Learn SQL

OK, since you comprehend what SQL is, here are a few approaches to learning it.


Udemy is a video-based stage with a huge load of valuable classes you can take, and has more than 5,300 classes that include SQL somehow or another. Classes range from allowed to around $200, and more than 1,100 of the SQL seminars on Udemy are appraised four stars (out of five) or higher.


Microsoft has since quite a while ago had an enthusiasm for SQL; for instance, it concocted Microsoft SQL Server, a social information base administration framework utilised (in numerous varieties) by an assortment of organisations. While more seasoned forms were for on-premises work, later and particular versions of SQL Server work with the cloud (explicitly, Microsoft Azure SQL Database).

That is each of the ways that Microsoft knows SQL, and its Learn entryway offers a lot of documentation with that impact—there’s beginning and end from a SQL apparatus outline to information base plan.

For those genuine about taking in SQL from the beginning, Microsoft’s SQL instructional class takes you from tenderfoot through master. It’s an aspect of the organisation’s MCSA (Microsoft Certified Solutions Associate) accreditation program, and a substantially more formal and clear approach to learn SQL. Given the number of organisations dependent on Microsoft’s interpretation of SQL, it’s imperative to acquaint yourself with it.

W3 Schools:

In the event that you learn best by executing what you’re realising straight away, W3Schools is an extraordinary stage to begin your excursion: It highlights models, broad breakdowns of SQL’s essentials, and the sky’s the limit from there.

We will alert that W3Schools drops you into SQL hot, so be set up to become familiar with the center components rapidly (and bomb quick). The best relationship is being tossed into the most profound finish of the pool: You will figure out how to swim at a quickened rate, to say the least.

 What Can SQL do?

  • SQL can run questions against a database of knowledge
  • SQL will recover data from a data set,
  • In a knowledge base, SQL will embed records
  • In a knowledge base, SQL can refresh records in
  • SQL can delete records from a database of knowledge.
  • SQL will build fresh databases
  • In a knowledge base, SQL can render fresh relations
  • In a knowledge base, SQL will delete systems
  • In a knowledge base, SQL can make visits
  • On relations, methodology, and viewpoints, SQL will set permissions

Using SQL in Your Web Site

To build a site that presents data from a knowledge base, you would need:

  • A database software for RDBMS knowledge (for example, MS Access, SQL Server, MySQL)
  • Using a worker-side scripting language such as PHP or ASP
  • To use SQL to get the specifics you need,
  • Use HTML / CSS to style a website


RDBMS is known as Relational Database Management System.

For SQL and for all specialised knowledge base systems, such as MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access, RDBMS is the reason.

The RDBMS information is contained in elements of the data collection called relations. A relation is a collection of linked passages of material that consists of divisions which columns.

Take a gander at the ” Employee ” relation:


SELECT * FROM Employee;

Each relation is separated into more modest elements called meadows. The meadows in the Employee relation comprise of EmployeeID, EmployeeName, EmployeeName, Address, City, Postal Code and Country. A meadow is a section in a relation that is intended to keep up explicit data about each record in the relation.

A record, additionally called a line, is every individual section that holds in a relation. For instance, there is 91 evidence in the above Employee relation. Evidence is an even element in a relation.

A section is a vertical element in a relation that consists of all data related to a particular meadow in a relation.

Some of The Most Important SQL Commands:

  • SELECT – removes information from a data set
  • UPDATE – refreshes information in a data set
  • Erase – erases information from a data set
  • Addition INTO – embeds new information into a data set
  • Make DATABASE – makes another information base
  • Modify DATABASE – adjusts an information base
  • Make RELATION – makes another relation
  • Modify RELATION – adjusts a relation

Why is SQL the most Important?

SQL is extensively renowned considering the way that it offers the going with focal points

  • Grants customers to get to data in the social database organisation systems.
  • Grants customers to portray the data.
  • Grants customers to describe the data in a database and control that data.
  •  Grants to introduce inside various vernaculars using SQL modules, libraries and pre-compilers.
  •  Grants customers to make and drop databases and relations.
  • Grants customers to make see, taken care of technique, limits in a database.
  • Licenses customers to set approvals on relations, techniques and viewpoints.

SQL Process:

At the point of executing a SQL order for any RDBMS, the system determines the most ideal solution to your request and some way to decode the errand is sorted by the SQL engine.

For this cycle, various pieces are recalled.

  • These parts are
  •  Inquiry courier
  •  Advancement appliance
  •  Exemplary Engine Query
  •  SQL Query Engine, and so on

Following is a straightforward outline demonstrating the SQL Architecture

Straightforward outline demonstrating the SQL Architecture
(Source: https://www.tutorialspoint.com/sql/sql-overview.htm)

What is a NULL value?

In a partnership, a NULL reward is a reward in a meadow that gives an appearance of being clear, meaning that a meadow with a NULL benefit is a meadow of no merit. It is important to note that a NULL value is not necessarily the same as a zero value or a meadow containing spaces. A meadow with a NULL value is the one left transparent after the formation of a record.

SQL Constraints

The specifications are the criteria imposed on the pages of knowledge on a partnership. These are used to regulate the type of data that may go into a relationship. It ensures the quality and durability of the information found in the information base.

Section level or partnership level criteria may be either. Segment level constraints, however, are uniquely applicable to one section; relationship level imperatives are applicable to the whole relationship.

Following are probably the most regularly utilised imperatives accessible in SQL

  • NOT NULL Constraint − Ensures that a section can’t have a NULL worth.
  • DEFAULT Constraint − Provides a default motivation for a segment when none is demonstrated.
  • Exceptional Constraint − Ensures that all the characteristics in a segment are one of a kind.
  • Fundamental Key − Uniquely recognises every segment/record in a database connection.
  • New Key − Uniquely recognises a section/record in any other database connection.
  • CHECK Constraint − The CHECK necessity ensures that all characteristics in a part satisfy certain conditions.
  • Document − Used to make and recuperate data from the database quickly.

Data Integrity

The accompanying classifications of information uprightness exist with each RDBMS

  • Area Integrity-Enforces valid parts by restricting the type, structure, or scope of characteristics for a given portion.
  • Referential trustworthiness: Rows used for multiple documents should not be discarded.

SQL Optimization

Realising how to make inquiries isn’t excessively troublesome, however you have to truly learn and see how information stockpiling functions, and how questions are perused so as to upgrade SQL execution. Enhancements depend on two key variables:

  • Settling on the correct decisions when characterising the information base structure
  • Applying the most suirelation strategies to peruse the information.

Reasons for incompatibility in SQL

There are a few explanations behind this absence of compactness between information base frameworks:

  • The unpredictability and size of the SQL standard implies that most practitioners don’t uphold the whole norm.
  • The standard doesn’t indicate information base conduct in a few significant zones (for example records, document stockpiling), leaving executions to conclude how to carry on.
  •  The SQL standard accurately indicates the sentence structure that an adjusting information base framework must execute. Be that as it may, the standard’s detail of the semantics of language builds is less all around characterised, prompting equivocalness.
  • Numerous information base sellers have enormous existing client bases; where the more current form of the SQL standard clashes with the earlier conduct of the merchant’s information base, the seller might be reluctant to break in reverse similarity.
  • There is minimal business motivating force for merchants to make it simpler for clients to change information base providers (see seller lock-in).
  • Clients assessing information base programming will in general place different factors, for example, execution higher in their needs than norms conformance.

Relational databases and SQL

For what reason would you surrender a factor of two improvements in execution speed and memory use? There were two central reasons: simplicity of improvement and convey ability. I didn’t think it is possible that one made a difference much in 1980 contrasted with execution and memory prerequisites, however as PC equipment improved and became less expensive individuals quit thinking about execution speed and memory and stressed more over the expense of advancement.

All in all, Moore’s Law slaughtered CODASYL information bases for social data sets. As it occurred, the improvement being developed time was critical, however SQL convenience ended up being an unrealistic fantasy.

Where did the social model and SQL originate from? E.F. “Ted” Codd was a PC researcher at the IBM San Jose Research Laboratory who worked out the hypothesis of the social model during the 1960s and distributed it in 1970. IBM was delayed to actualise a social information base with an end goal to secure the incomes of its CODASYL data set IMS/DB. At the point when IBM at long last began its System R venture, the improvement group (Don Chamberlin and Ray Boyce) wasn’t under Codd, and they overlooked Codd’s 1971 Alpha social language paper to plan their own language, SEQUEL (Structured English Query Language). In 1979, preceding IBM had even delivered its item, Larry Ellison consolidated the language in his Oracle information base (utilising IBM’s pre-dispatch SEQUEL distributions as his spec). Continuation before long became SQL to keep away from a worldwide brand name infringement.

The “tom-toms beating for SQL” (as Michael Stonebreaker put it) were coming from Oracle and IBM, yet additionally from clients. It was difficult to recruit or prepare CODASYL information base fashioners and developers, so SEQUEL (and SQL) looked substantially more appealing. SQL was so appealing in the later 1980s that numerous information base sellers basically stapled a SQL inquiry processor on head of their CODASYL information bases, to the incredible disappointment of Codd, who felt that social data sets must be planned without any preparation to be social.

An unadulterated social information base, as planned by Codd, is based on tuples assembled into relations, steady with first-request predicate rationale. Genuine social information bases have relations that contain meadows, requirements, and triggers, and relations are connected through unfamilikeys. SQL is used to pronounce the information to be returned, and a SQL inquiry processor and question analyser transform the SQL assertion into an inquiry plan that is executed by the information base motor.

SQL incorporates a sub-language for characterising compositions, the information definition language (DDL), alongside a sub-language for changing information, the information control language (DML). Both of these have been established in early CODASYL determinations. The third sub-language in SQL proclaims questions, through the SELECT articulation and social joins.

SQL SELECT statement:

The SELECT articulation advises the inquiry enhancer what information to restore, what relations to glance in, what relations to follow, and what request to force on the brought information back. The inquiry analyzer needs to sort out without anyone else what records to use to dodge beast power relation outputs and accomplish great question execution, except if the specific information base backings file hints.

Part of the specialty of social information base plan holds tight the wise utilisation of files. On the off chance that you discard a list for an incessant inquiry, the entire information base can back off under weighty read loads. In the event that you have too many lists, the entire information base can back off under substantial compose and update loads.

Another significant workmanship is picking a decent, remarkable essential key for each relation. You do not just need to think about the effect of the essential key on regular questions, however how it will play in joins when it shows up as an unfamiliar key in another relation, and how it will influence the information’s area of reference.

In the serious instance of information base relations that are separated into various volumes relying upon the estimation of the essential key, called flat sharding, you likewise need to consider how the essential key will influence the sharding. Clue: You need the relation appropriated equally across volumes, which recommends that you would prefer not to utilise date stamps or continuous whole numbers as essential keys.

Google Analytics and SQL:

Google Analytics is an extremely mainstream device among site and blog proprietors the same. With a straightforward and speedy arrangement, it lets you assemble information about your site page guests without any problem. Nonetheless, did you realise that you can send out information from Google Analytics to make your own SQL reports? Peruse this article to discover how. Google Analytics is an incredibly well known and amazing arrangement that allows you to gather and examine different sorts of data about your site.

How to Create Your First Relation in SQL?

Making an information base relation with SQL is one of the center abilities you’ll have to work with information. What’s more, it’s anything but difficult to learn, so we should begin! Envision you’re examining information and need to store your outcomes in an information base relation. Without a doubt, you’ve done this multiple times in Excel. However, you don’t know how to make a relation with SQL. Or then again perhaps you’ve seen that information designing is popular and you need to begin learning its center ideas.

How to Join the Same Relation Twice?

JOIN is one of the most widely recognised explanations in SQL. As you may know, it is utilised to join and consolidate information from at least two relations into one regular informational index. In this article, I will examine uncommon kinds of joins? in which you consolidate a similar relation twice including joining a relation to itself, otherwise called oneself join. When and for what reason do you have to do this?

What Is the MySQL OVER Clause?

In 2018, MySQL presented another element: window capacities, which are gotten to by means of the OVER condition. Window capacities are an overly ground-breaking asset accessible in practically all SQL information bases. They play out a particular computation (for example whole, tally, normal, and so on) on a lot of lines; this arrangement of lines is known as a “window” and is characterised by the MySQL OVER statement.


In other words, we can say that Organised/structured Query Language (SQL) is a programming language used to oversee information in a social data set. SQL can be utilised to alter, embed and erase different records on the double, notwithstanding different capacities, and is the standard language utilised for social information base questions. While SQL has been embraced as the norm, numerous usage has interesting highlights or excludes portions of the SQL execution, which can make them contrary with each other.


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