<!DOCTYPE html>undefined
<html>undefined
<body>undefined
<h1>My first Heading</h1>undefined
<p>My first paragraph</p>undefined
</body>undefined
</html> undefinedundefinedThe undefined<!DOCTYPE> declaration represents the document type, and helps browsers to display web pages correctly. It must only appear once, at the top of the page (before any HTML tags). The undefined<!DOCTYPE> declaration is not case sensitive. undefined
HTML headings are defined with the undefined<h1> to undefined<h6> tags. undefined<h1>defines the most important heading. undefined<h6> defines the least important heading:undefined
undefined<h1>Big</h1>undefined
undefined<h6>Small</h6>undefined
HTML paragraphs are defined with the <p> tag:undefinedundefinedundefined
<p>This is a paragraph.</p>undefined
<p>This is another paragraph.</p>undefined
HTML links are defined with the <a> tag:undefined
undefined<a href="https://example.com">This is a link</a>undefined
HTML images are defined with the <img> tag. The source file (src), alternative text (alt), width, and height are provided as attributes:undefined
undefined<img src="example.jpg" alt="example.com" width="104" height="142">undefined
undefined h1 {undefinedundefined
color: black;undefined
text-align: center;undefined
font-size: 26px;undefined
font-family: verdana;undefined
} undefined
undefined<p style="font-size:10px">undefined
To put CSS files in HTML, use: undefined
undefined<link rel="stylesheet" href="style.css">undefined
To put CSS code in HTML, use: undefined
undefined <style>undefinedundefined
.class {undefined
}undefined
</style> undefined
Selector
undefinedp { undefinedProperty
undefined color: red; undefinedDeclaration
undefined}undefinedundefinedProperties - With these, you can style a HTML element, like for example; color. undefined
undefinedProperty Value - This chooses one of the possible options for a given property, like red for color.undefined
You can also write CSS like undefinedhtml{color:red;}undefined
You can also put styles in HTML elements. undefined<h1 style="font-color:white;">undefined
You can also select multiple elements at once like... undefined
undefined h1, h4, h6, h2 { color: red; }undefined
Think of classes like custom HTML elements, they can be applied in html like undefined<p class="text-red">undefined
Classes begin with a dot or period (.) to begin the selector.
undefinedundefined .text-red {undefinedundefined
undefinedfont-size: 10px; - Text size, can be in pixels.undefined
undefinedfont-family: verdana; - Fontsundefined
undefinedtext-align: center; - Can align to the left side, right side, or in the center of the webpage. undefined
undefinedtext-shadow: 3px black - Shadow of text. It can be in pixels and colors. undefined
undefinedpadding-top: 50px; - Separation. It can be top, left, right, and bottom in pixels.undefined
undefinedmargin: 50px; - A margin. It can be in pixels.undefined
undefinedborder-width: 5px; - Border width. Can be thin, medium, thick, or just pixels.undefined
undefinedborder-style: dotted; - Border style. Can be dotted, dashed, solid, double, groove, ridge, inset, outset, none, or hidden. Can also be colored.undefined
undefinedwidth=500px; - Width of the element. It can be pixels or percentages.undefined
undefinedcolor: red; - The color of the element, can be hexadecimal, or RGB.undefined
undefinedbackground-color: white; - Background color of the element.undefined
Comments are commonly used to explain the code and may help when you edit the source code later and are ignored by browsers. undefined
undefined
A CSS comment starts with undefined/* and ends with undefined*/, and no changes are needed to make it multiple lines.undefined
undefined /* This is a single-line comment */undefinedundefined
undefined
/* This isundefined
a multi-lineundefined
comment */undefined
undefinedimg { margin: 0 auto; display: block; }undefined
undefined<script type="text/javascript"> undefinedundefined
//JS code goes here undefined
</script> undefined
undefined<script src="myscript.js"></script>undefined
Single line comments - undefined// Commentundefined
Multi-line comments - undefined/* comment here */undefined
undefinedvar, const, letundefined
undefinedvar — The most common variable. It can be reassigned but only accessed within a function. Variables defined with var move to the top when code is executed.undefined
undefinedconst — Can not be reassigned and not accessible before they appear within the code.undefined
undefinedlet — Similar to const, however, let variable can be reassigned but not re-declared.undefined
undefined
Numbers — undefinedvar age = 23undefined
Variables — undefinedvar xundefined
Text (strings) — undefinedvar a = "init"undefined
Operations — undefinedvar b = 1 + 2 + 3undefined
True or false statements — undefinedvar c = trueundefined
Constant numbers — undefinedconst PI = 3.14undefined
Constant numbers — undefinedconst PI = 3.14undefined
Objects — undefinedvar name = {firstName: "John", lastName: "Doe"}undefined
undefinedObjects Exampleundefined
undefined
-
++ + + + ++Example Document
++<!DOCTYPE html>
+<html>
+ <body>
+ <h1>My first Heading</h1>
+ <p>My first paragraph</p>
+ </body>
+</html> +
+The
+<!DOCTYPE>declaration represents the document type, and helps browsers to display web pages correctly. It must only appear once, at the top of the page (before any HTML tags). The<!DOCTYPE>declaration is not case sensitive.++HTML Headings
+HTML headings are defined with the
+<h1>to<h6>tags. +<h1>defines the most important heading.<h6>defines the least important heading:
+<h1>Big</h1>
+<h6>Small</h6>++HTML Paragraphs
+HTML paragraphs are defined with the <p> tag:
+
+<p>This is a paragraph.</p>
+<p>This is another paragraph.</p>++HTML Links
+HTML links are defined with the <a> tag:
+
+<a href="https://example.com">This is a link</a>++HTML Images
+HTML images are defined with the <img> tag. The source file (src), alternative text (alt), width, and height are provided as attributes:
+
+<img src="example.jpg" alt="example.com" width="104" height="142">+ + + + + ++Example Document
++
++h1 {
+ color: black;
+ text-align: center;
+ font-size: 26px;
+ font-family: verdana;
+} ++
<p style="font-size:10px">To put CSS files in HTML, use: +
+<link rel="stylesheet" href="style.css">To put CSS code in HTML, use: +
+
++<style>+
+.class {
+}
+</style> +++CSS Rulesets
++
+Selector
p {+Property
color: red;+ +Declaration
}Properties - With these, you can style a HTML element, like for example; color.
+
+Property Value - This chooses one of the possible options for a given property, like red for color.+You can also write CSS like
+html{color:red;}+
+You can also put styles in HTML elements.<h1 style="font-color:white;">+
+You can also select multiple elements at once like... +
++h1, h4, h6, h2 { + color: red; +}++Classes
+Think of classes like custom HTML elements, they can be applied in html like
+<p class="text-red">Classes begin with a dot or period (.) to begin the selector.
++
+.text-red {++ color: red; +} ++Text Elements
+
+font-size: 10px;- Text size, can be in pixels.
+font-family: verdana;- Fonts
+text-align: center;- Can align to the left side, right side, or in the center of the webpage.
+text-shadow: 3px black- Shadow of text. It can be in pixels and colors. +++Padding Elements
++
+padding-top: 50px;- Separation. It can be top, left, right, and bottom in pixels.
+margin: 50px;- A margin. It can be in pixels.
+border-width: 5px;- Border width. Can be thin, medium, thick, or just pixels.
+border-style: dotted;- Border style. Can be dotted, dashed, solid, double, groove, ridge, inset, outset, none, or hidden. Can also be colored.
+width=500px;- Width of the element. It can be pixels or percentages.++Color Elements
++
color: red;- The color of the element, can be hexadecimal, or RGB.
+background-color: white;- Background color of the element.++Comments
+Comments are commonly used to explain the code and may help when you edit the source code later and are ignored by browsers. +
+
+A CSS comment starts with/*and ends with*/, and no changes are needed to make it multiple lines.+
+ /* This is a single-line comment */
+ /* This is
+a multi-line
+ comment */++Extra: Centering Images
++
img { + margin: 0 auto; + display: block; +}undefined + undefinedundefined + undefined++Including JavaScript in an HTML Page
++
<script type="text/javascript">
+ //JS code goes here
+</script>++Call an External JavaScript File
++
<script src="myscript.js"></script>++Including Comments
+Single line comments -
+// Comment
+Multi-line comments -/* comment here */++Variables
++
+var, const, let
+var— The most common variable. It can be reassigned but only accessed within a function. Variables defined with var move to the top when code is executed.
+const— Can not be reassigned and not accessible before they appear within the code.
+let— Similar to const, however, let variable can be reassigned but not re-declared.
++undefinedData Types
++Numbers —
+ +var age = 23
+Variables —var x
+Text (strings) —var a = "init"
+Operations —var b = 1 + 2 + 3
+True or false statements —var c = true
+Constant numbers —const PI = 3.14
+Constant numbers —const PI = 3.14
+Objects —var name = {firstName: "John", lastName: "Doe"}+Objects Example
+var person = { firstName: "John", lastName: "Doe", age: 20, nationality: "American" } -undefinedundefined -undefined undefinedundefined undefinedundefined undefinedundefined undefinedundefinedundefinedQuerying Data from a Table
undefinedQuery Data in Columns c1, c2 from a Table
undefinedSELECT c1, c2 FROM t;undefinedundefined
Code language: SQL (Structured Query Language) (SQL) undefined
undefined
undefinedQuery All Rows and Columns from a Table
undefinedSELECT * FROM t;undefined
undefined
undefinedQuery Data and Filter Rows with a Condition
undefinedSELECT c1, c2 FROM tundefinedundefined
WHERE condition; undefined
undefined
undefinedQuery Distinct Rows from a Table
undefinedSELECT DISTINCT c1 FROM tundefinedundefined
WHERE condition; undefined
undefined
undefinedSort the Result Set in Ascending or Descending Order
undefinedSELECT c1, c2 FROM tundefinedundefined
ORDER BY c1 ASC [DESC]; undefined
undefined
undefinedSkip Offset of Rows and Return the Next n Rows
undefinedSELECT c1, c2 FROM tundefinedundefined
ORDER BY c1undefined
LIMIT n OFFSET offset; undefined
undefined
undefinedGroup Rows using an Aggregate Function
undefinedSELECT c1, aggregate(c2)undefinedundefined
FROM tundefined
GROUP BY c1; undefined
undefined
undefinedFilter Groups using undefinedHaving Clauseundefined
undefinedSELECT c1, aggregate(c2)undefinedundefined
FROM tundefined
GROUP BY c1undefined
HAVING condition; undefined
undefined
undefinedundefinedundefinedModifying Data
undefinedInsert One Row into a Table
undefinedINSERT INTO t(column_list)undefinedundefined
VALUES(value_list); undefined
undefined
undefinedInsert Multiple Rows into a Table
undefinedINSERT INTO t(column_list)undefinedundefined
VALUES (value_list), undefined
(value_list), …; undefined
undefined
undefinedInsert Rows from t2 into t1
undefinedINSERT INTO t1(column_list)undefinedundefined
SELECT column_listundefined
FROM t2; undefined
undefined
undefinedUpdate New Value in the Column c1 for All Rows
undefinedUPDATE tundefinedundefined
SET c1 = new_value; undefined
undefined
undefinedUpdate Values in the Column c1, c2 that Match the Condition
undefinedUPDATE t SET c1 = new_value, undefinedundefined
c2 = new_valueundefined
WHERE condition; undefined
undefined
undefinedDelete All Data in a Table
undefinedDELETE FROM t;undefinedDelete Subset of Rows in a Table
undefinedDELETE FROM tundefinedundefined
WHERE condition; undefined
undefined
undefinedundefinedundefinedTable Management
undefinedCreate a new Table with Three Columns
undefinedCREATE TABLE t (undefinedundefined
id INT PRIMARY KEY,undefined
name VARCHAR NOT NULL,undefined
price INT DEFAULT 0undefined
);undefined
undefined
undefined
undefinedDelete the Table from the Database
undefinedDROP TABLE t ;undefined
undefined
undefinedAdd a new Column to the Table
undefinedALTER TABLE t ADD column;undefined
undefined
undefinedDrop Column c from the Table
undefinedALTER TABLE t DROP COLUMN c ;undefined
undefined
undefinedAdd a Constraint
undefinedALTER TABLE t ADD constraint;undefined
undefined
undefinedDrop a Constraint
undefinedALTER TABLE t DROP constraint;undefined
undefined
undefinedRename a Table from t1 to t2
undefinedALTER TABLE t1 RENAME TO t2;undefined
undefined
undefinedRename Column c1 to c2
undefinedALTER TABLE t1 RENAME c1 TO c2 ;undefined
undefined
undefinedRemove all Data in a Table
undefinedTRUNCATE TABLE t;undefinedundefined undefined - undefined - undefined -undefined undefinedundefined undefinedundefined undefinedundefinedundefinedExample Document
undefined{undefinedundefined
"foo": "bar", "array": [ "foo", "bar" ]undefined
} undefined
undefined
undefinedAll JSON files are surrounded by { and }, which means it is a object. Unlike Javascript, you must use double quotes (") for strings, not singular quotes (')
undefinedundefinedundefinedImporting JSON
undefinedundefinedundefined
undefinedundefined undefinedJavaScript undefinedundefined undefinedfetch('example.json')undefinedundefined undefinedNode.js undefinedundefined undefinedimport('./example.json')undefinedundefined undefinedTypeScript + Node.js undefinedundefined undefinedimport data from 'example.json'undefinedundefined undefinedundefinedPython undefinedundefined undefinedimport 'json'; with open('data.json', 'r') as f: data = json.load(f)undefinedundefined -
Query Data in Columns c1, c2 from a Table
+
+SELECT c1, c2 FROM t;
+Code language: SQL (Structured Query Language) (SQL)
+Query All Rows and Columns from a Table
+SELECT * FROM t;Query Data and Filter Rows with a Condition
+
+SELECT c1, c2 FROM t
+WHERE condition;
+Query Distinct Rows from a Table
+
+SELECT DISTINCT c1 FROM t
+WHERE condition;
+Sort the Result Set in Ascending or Descending Order
+
+SELECT c1, c2 FROM t
+ORDER BY c1 ASC [DESC];
+Skip Offset of Rows and Return the Next n Rows
+
+SELECT c1, c2 FROM t
+ORDER BY c1
+LIMIT n OFFSET offset;
+Group Rows using an Aggregate Function
+
+SELECT c1, aggregate(c2)
+FROM t
+GROUP BY c1;
+Filter Groups using Having Clause
+
+SELECT c1, aggregate(c2)
+FROM t
+GROUP BY c1
+HAVING condition;
+Insert One Row into a Table
+
+INSERT INTO t(column_list)
+VALUES(value_list);
+Insert Multiple Rows into a Table
+
+INSERT INTO t(column_list)
+VALUES (value_list),
+ (value_list), …;
+Insert Rows from t2 into t1
+
+INSERT INTO t1(column_list)
+SELECT column_list
+FROM t2;
+Update New Value in the Column c1 for All Rows
+
+UPDATE t
+SET c1 = new_value;
+Update Values in the Column c1, c2 that Match the Condition
+
+UPDATE t
+SET c1 = new_value,
+ c2 = new_value
+WHERE condition;
+Delete All Data in a Table
+DELETE FROM t;
+Delete Subset of Rows in a Table
+
+DELETE FROM t
+WHERE condition;
+Create a new Table with Three Columns
+
+CREATE TABLE t (
+ id INT PRIMARY KEY,
+ name VARCHAR NOT NULL,
+ price INT DEFAULT 0
+);
+Delete the Table from the Database
+DROP TABLE t ;Add a new Column to the Table
+ALTER TABLE t ADD column;Drop Column c from the Table
+ALTER TABLE t DROP COLUMN c ;Add a Constraint
+ALTER TABLE t ADD constraint;Drop a Constraint
+ALTER TABLE t DROP constraint;Rename a Table from t1 to t2
+ALTER TABLE t1 RENAME TO t2;Rename Column c1 to c2
+ALTER TABLE t1 RENAME c1 TO c2 ;Remove all Data in a Table
+TRUNCATE TABLE t;
+
+{
+ "foo": "bar",
+ "array": [
+ "foo",
+ "bar"
+ ]
+}
+All JSON files are surrounded by { and }, which means it is a object. Unlike Javascript, you must use double quotes (") for strings, not singular quotes (')
+| JavaScript | +fetch('example.json') |
+
| Node.js | +import('./example.json') |
+
| TypeScript + Node.js | +import data from 'example.json' |
+
| Python | +import 'json'; with open('data.json', 'r') as f: data = json.load(f) |
+