Y9 All Computer Science [end of years revision]

All topics covered in Y9 computer science: databases, python, logic gates

Table

a collection of related data sorted in an organized way. Made up of fields and records

Record

all of the data relating to one instance of the table, represented by a row e.g. Sophia Austin

(don’t say that it is a row)

Field

an attribute which all records have in common, represented by a column e.g. date of birth

(don’t say it is a column)

Query

a request for information - a way to access information from a database

Primary key

a special field that stores a unique value (an ID) for each record

CREATE TABLE statement line 1

 CREATE TABLE table_name (

‘CREATE TABLE’ and the table name, then open brackets

CREATE TABLE statement lines for fields

	text_field_name VARCHAR(30),
 	text_field_name VARCHAR(30),
	integer_field_name INT,
	decimal_field_name FLOAT,
	true_or_false_field_name BOOLEAN

(indented)

Name of your first field (column), and after it what type of data you’ll be entering in it, e.g. text or numbers. For a text field you need to say how many characters it should allow as maximum. You put this number in brackets

Repeat for all the fields in the table

CREATE TABLE statement last line

	);

This closes off the list

INSERT INTO statement first line

INSERT INTO table_name

‘INSERT INTO’ and then your table name

INSERT INTO statement second line

VALUES	

INSERT INTO statement lines for values

("Text 1",44,55,33,1),
("Text 2",77,11,99,0),
("Text 3",29,100,21,8)

write a list of values to put into your table, each line is one record (row), and each field is separated by commas

quotes around any text data

INSERT INTO statement last line

;

SELECT FROM statement first line

SELECT * FROM table_name;

‘SELECT * FROM’ and then your table name and a ;

SELECT Firstname,Email FROM table4

What will this give you

All the firstnames and emails from table4

SELECT table4.Firstname, table4.email

What will this give you

All the firstnames and emails from table4

This is just another way of doing it, specifying each time which table you want it from instead of once at the start

SELECT Firstname FROM table_name WHERE surname="abe";

What will this give you

will give you all the firstnames in the table that have surnames containing ‘abe’, but not the surname

if you want it to display that you have to put it after a comma next to the firstname

function of => (SQL)

greater than or equal to

function of <= (SQL)

less than or equal to

function of <> (SQL)

not equal to

SQL: VARCHAR data type

a string of variable length (can contain letters, numbers and special characters). After it you put the maximum character length in brackets

SQL: INTEGER (aka INT) data type

a number

SQL: DECIMAL data type

an exact number with a fixed amount of digits and a fixed amount of digits after the decimal point, written as DECIMAL(digits, digits after decimal point)

SQL: BOOLEAN (aka BOOL) data type

true or false, 0 is false and anything else it true

Variable

a named memory location, used to store a value while the program is running. The value can change whilst the program runs

Operator

a symbol that takes one or more values and yields another value e.g. addition

Python: string data type

text

Python: integer (int) data type

number(s)

Python: float data type

a decimal

Python: boolean data type

true or false

1 = true
0 = false

* maths operator (python)

multiplication

** maths operator (python)

to the power of

// maths operator (python)

division, rounds the result down to the nearest whole number

% maths operator (python)

gives you the remainder of the first number divided by the second

== operator (python)

equal (not with numbers)

!= operator (python)

≠ (not equal to)

NOT gate

gives the opposite of what was put into it

AND gate

needs both inputs to be 1 to have an output of 1, anything else will give 0

OR gate

Will give 1 if either or both imputs are 1, will give 0 if both are 0

Definite iteration

when a code is repeated a specific number of times (for loop)

Indefinite iteration

when a code is repeated until a condition is met/no longer met

Iterating over a list

printing every item in that list

Range function (python)

prints every number in the range you specified (not including the number that you put, including 0)