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ICT

Database

Data types

Structure

Concepts

SQL Syntax

SELECT field1, field2, ...
FROM table_name

For fields, * can be used for all fields

Where

Condition, used for filtering records.

SELECT field1, field2, ...
FROM table_name
where condition

Operators:

Operator Example
= str = 'TEXT' num = 1
<> Num <> 1
> < >= <= num > 1
LIKE str LIKE 'ab_d%'
IN str IN ('a', 'b', 'c')
AND OR NOT num < 10 OR num > 100

For LIKE, _ stands for 1 character, while % stands for 0+ characters.

For IN, the set after it can be another SELECT command.

GROUP BY

SELECT column_name(s)
FROM table_name
GROUP BY column_name(s)

Group the rows with the same column value into groups.

Order by

SELECT field1, field2, ...
FROM table_name
ORDER BY field1, field2,... ASC|DESC

If field1 equals, check field2. If all equal, use the order stored in the table

Functions

Note that if used with GROUP BY, these function will process the rows in each group instead of all the rows at once.

Integrated use of a software suite

Concepts

Networking

Concepts

Hardware

Protocol

IP Class

Class Number Class Network address Host address Number of host
0 A 1 byte 2-4 byte 16,777,217
10 B 1-2 byte 3-4 byte 65,534
110 C 1-3 byte 4 byte 254

Class number is the bits at the beginning of the IP.
For network address, class number need to be removed
Host address of all 0s and 1s are reserved.

Domain name

Uniform resource locator (URL)

Protocol://DomainName/path:port
Ex: https://apis.google.com/js/rpc.js

Default port 80

Multimedia File Formats

Bitmap format Characteristic
BMP Large, original color, uncompressed
JPG/JPEG Widely used. highly compressed, full-colour, lossy
GIF Simple colour, transparent background, animation
PNG small file size, millions of color, progressive rendering, opacity control
Vector format Characteristic
SWF Flash, animated
WMF Windows based, cannot be edited extensively
EPS Widely used
SVG Used in web, based on XML
Audio format Characteristic
WAV Lossless, uncompressed
WMA support streaming, popular
MP3 support streaming, widely used in portable players, popular
AAC support streaming, Lossy compressed, popular

Video formats(All support streaming):

HTML

Tag syntax

Tag: <tagName attribute1="value" attribute2="value"...>element in it</tagName>

Single tag: <tagName attribute1="value" attribute2="value"...>

HTML structure

Algorithm

Concepts