PHP variable declaration

$variable = 1;

JS alternative

let variable = 1;

PHP - check if the variable exists

if (isset($variable))

JS alternative

if (typeof variable !== "undefined")

PHP count array elements

$count = count([2, 3, 4]);

JS alternative

let count = [2, 3, 4].length;

PHP count letters in the string

$len = strlen('some string');

JS alternative

let len = 'some string'.length;

PHP absolute value of a given number

$variable = abs(-5);

JS alternative

let variable = Math.abs(-5);

PHP - power of a number

$square = pow(5, 2);

JS alternative

let square = Math.pow(5, 2);

PHP - square root of a number

$square_root = sqrt(16);

JS alternative

let square_root = Math.sqrt(16);

PHP - minimum number

$max = min(2, 3, 4);

JS alternative

let max = Math.min(2, 3, 4);

PHP - maximum number

$max = max([2, 3, 4]);

JS alternative

let max Math.max(...[2, 3, 4])

PHP calculates sum of the array elements

$sum = array_sum([2, 3, 4]);

JS alternative

let sum = 0;
let arr = [1, 2, 3];
for (let value of arr) {
    sum += value;
}

Another way to calculate the same

let arr = [1, 2, 3];
let sum = 0;
let len = arr.length;
for (let i = 0; i < len; sum += arr[i++]);

PHP - string position

$pos = strpos('Hello world', 'world');

JS alternative

let pos = 'Hello world'.indexOf('world');

PHP - edit letter in a string

$string[4] = 'X';

JS alternative

string = string.substring(0, 4) + 'X' + string.substring(5);

PHP convert the variable to integer

$variable = intval(5.5);

JS alternative

let variable = parseInt(5.5);

PHP - explode the sentence

$sentence = "Lorem ipsum dolor st amet";
$words = explode(" ", $sentence);

JS alternative

let sentence = "Lorem ipsum dolor st amet";
let words = sentence.split(" ");

The git merge --squash command combines changes from one branch into another branch but does not create a merge commit. Step 1: Initialize project

git init

Step 2: create index.html file and 2 commit m1,m2 add text "m1" into index.html and commit as m1

echo "m1" > index.html
git add .
git commit -m "m1" 

add text "m2" into index.html and commit as m2

echo "m2" >> index.html
git add .
git commit -m "m2" 

Step 3: create feature branch and checkout

git checkout -b feature

Step 4: create feature folder&file create feature.html into the feature folder and add text "f1" then commit as f1

echo "f1" >> feature/feature.html
git add .
git commit -m "f1" 

Step 5: Checkout to master

git checkout master

Step 6: add text "m3" into index.html and commit as m3

echo "m3" >> index.html
git add .
git commit -m "m3" 

Step 7: Checkout to feature

git checkout feature

Step 8: add text "f2" into feature.html and commit as f2

echo "f1" >> feature/feature.html
git add .
git commit -m "f2" 

Step 9: Checkout to master

git checkout master

Step 10: Merge feature branch into master with squash

git merge --squash feature

Step 11: See git status because files we will have into the staging area and we need create a commit for it

git status
git commit -m "Merge feature branch into master"

The new note

source 

code4123 new code line one more line1h

Trigger can run

before

or

after

some database event. The event can be

insert

,

update

or

delete

. It means there are six types of triggers:

before / after

insert

before / after

update

before / after

delete

Creates trigger that runs

before

insert

and checks & replaces gender values

DROP TRIGGER IF EXISTS before_student_insert;

DELIMITER $$

    CREATE TRIGGER before_student_insert BEFORE INSERT 
    ON students
    FOR EACH ROW 
    BEGIN

    INSERT INTO log (description)
    VALUES ('One student will be inserted');
    
    IF (NEW.gender = 'Female') THEN
        SET NEW.gender = 2;
    ELSE
        SET NEW.gender = 1;
    END IF;

    END$$

DELIMITER ;

MySQL supports several referential actions:

CASCADE

- deletes or updates appropriate rows in the child table

SET NULL

- sets the foreign key column of the child table to

NULL

RESTRICT

- rejects the operation for the parent table

NO ACTION

- equivalent to

RESTRICT

Note:

RESTRICT

is the same as omitting the

ON DELETE

or

ON UPDATE

clause, which means that it's default action

DROP FUNCTION IF EXISTS getIncomeLevel;

DELIMITER //

CREATE FUNCTION getIncomeLevel ( monthly_value INT )
RETURNS varchar(20)

BEGIN

   DECLARE income_level varchar(20);

   IF monthly_value <= 4000 THEN
        SET income_level = 'Low Income';
   ELSEIF monthly_value > 4000 AND monthly_value <= 7000 THEN
        SET income_level = 'Avg Income';
   ELSE
        SET income_level = 'High Income';
   END IF;

   INSERT INTO log (description)
   VALUES ('getIncomeLevel function was called');

   RETURN income_level;

END; //

DELIMITER ;

After creating the function we can call it:

SELECT getIncomeLevel(450)

DROP PROCEDURE IF EXISTS printIncomeLevel;

DELIMITER //

CREATE PROCEDURE printIncomeLevel (IN monthly_value INT)

BEGIN

   DECLARE income_level varchar(20);

   IF monthly_value <= 4000 THEN
        SET income_level = 'Low Income';
   ELSEIF monthly_value > 4000 AND monthly_value <= 7000 THEN
        SET income_level = 'Avg Income';
   ELSE
        SET income_level = 'High Income';
   END IF;

   INSERT INTO log (description)
   VALUES ('getIncomeLevel procedure was called');

   SELECT income_level;

END;

After creating the procedure, we can call it using

CALL

keyword:

CALL printIncomeLevel(450)

Creates one

INDEX

with several fields for table

notes

. Combines the two fields

title, description

to create one index

CREATE TABLE note (
    id int AUTO_INCREMENT,
    note_id int,
    title varchar(50),
    description varchar(50),
    PRIMARY KEY(id, note_id),
    INDEX ind_title_description (title, description)
);

If we need to filter the result with both fields

(title, description)

at the same time, then

ind_title_description

is a great index

Creates the table

note

and adds several indexes

(ind_note_id, ind_title_description)

at the same time

CREATE TABLE note (
    id int AUTO_INCREMENT,
    note_id int,
    title varchar(50),
    description varchar(50),
    PRIMARY KEY(id, note_id),
    INDEX ind_note_id (note_id),
    INDEX ind_title_description (title, description)
);