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Valeri Tandilashvili's Personal Professional Blog
Results: 1021
effect of changing main color using vriables
lighten 
.btn-a {
    background-color: lighten($beautifulHue, 45%);
}
@import / Splitting up code into smaller files
Includes .scss file. Example:
a {
    color: $beautifulHue;
}
@import 'header';
.btn-a {
...
@extend nested style
enable browser caching on digitalocean droplet
First, 
headers
and 
expires
modules must be enabled on the server:
sudo a2enmod headers 
sudo a2enmod expires
After that the server must be restarted:
service apache2 restart
Then it will work if 
.htaccess
contains the following:
# for enabling browser caching
<filesMatch ".(css|jpg|jpeg|png|gif|js|ico)$">
Header set Cache-Control "max-age=2592000, public"
</filesMatch>
css-minify
First 
css-minify
package must be installed 
globally
npm install css-minify -g
Installing globally is necessary. Before minify command is run, 
css-dist
directory must be created, where the output will be saved. The command: 
css-minify -f css/d1.css
will minify the specified .css file.
Nesting
Sass code:
.site-header nav {
    ul {
        padding: 0;
        margin: 0;
    }
    li {
        list-style: none;
        float: left;
    }
}
After Sass preprocessor:
.site-header nav ul {
    padding: 0;
    margin: 0;
}
.site-header nav li {
    list-style: none;
    float: left;
}
variables
Sass code:
$primaryColor: #ec7705;
a {
    color: $primaryColor;
}
After Sass preprocessor:
a {
    color: #ec7705;
}
SELECT statement
Selects all the fields from 
students
table (
*
means - all fields)
SELECT * 
FROM students
Selects only 
first_name
and 
last_name
from 
students
table (fields are separated by comma 
,
)
SELECT first_name, last_name 
FROM students
WHERE
clause in 
SELECT
statement
SELECT first_name, last_name 
FROM students
WHERE id = 5
WHERE
clause (combining several conditions with logical AND)
SELECT *
FROM students
WHERE points > 75 AND last_name = 'გელაშვილი'
WHERE
clause (combining several conditions with logical OR)
SELECT *
FROM students
WHERE last_name = 'გელაშვილი' OR last_name = 'გოგუაძე'
Logical OR with logical AND
SELECT *
FROM students
WHERE points > 75 AND (last_name = 'გელაშვილი' OR last_name = 'გოგუაძე')
ORDER BY
clause in 
SELECT
statement
SELECT first_name, last_name 
FROM students
ORDER BY id DESC
ORDER BY
last_name 
ascending
SELECT first_name, last_name 
FROM students
ORDER BY last_name ASC
ASC
is optional because it's default value 
ORDER BY
with several fields
SELECT first_name, last_name 
FROM students
ORDER BY last_name ASC, first_name ASC
ASC
SELECT
with some primitive values
SELECT first_name, last_name, 20 AS age 
FROM students
SELECT
with only primitive values
SELECT 20, 40 AS age 
FROM students
Math operations in 
SELECT
statement
SELECT 
    first_name, 
    last_name, 
    points * 1.1 /* + - * / % */ AS points
FROM students
Math operations in 
WHERE
clause
SELECT *
FROM students
WHERE points * 1.5 >= 80
Order of the Math operations matters
SELECT 
    first_name, 
    last_name, 
    (points + 10) * 2 AS points
FROM students
Advantages of quotes in alias
SELECT 
    first_name, 
    last_name, 
    (points + 10) * 2 AS 'points calculated'
FROM students
DISTINCT
keyword in SELECT statement
SELECT DISTINCT
    first_name, 
    last_name
FROM students
GROUP BY
clause with several fields (results of the two queries are identical)
SELECT 
    first_name, 
    last_name
FROM students
GROUP BY first_name, last_name
GROUP BY
clause with one field and 
COUNT()
function
SELECT 
    last_name,
    COUNT(last_name)
FROM students
GROUP BY last_name
GROUP BY
and 
ORDER BY
clauses in one select
SELECT 
    last_name,
    COUNT(last_name) last_name_counter
FROM students
GROUP BY last_name
ORDER BY last_name_counter DESC
LIMIT
clause
SELECT 
    last_name,
    COUNT(last_name) last_name_counter
FROM students
GROUP BY last_name
ORDER BY last_name_counter DESC
LIMIT 2
LIMIT
clause for pagination
SELECT 
    first_name
    last_name
FROM students
ORDER BY points DESC
LIMIT 4, 2
Student with minimum points
SELECT *
FROM students
ORDER BY points
LIMIT 1
Student with minimum points using 
MIN()
function
SELECT *
FROM students
WHERE points = (SELECT MIN(points) FROM students)
Student with maximum points
SELECT *
FROM students
ORDER BY points DESC
LIMIT 1
Student with maximum points using 
MAX()
function
SELECT *
FROM students
WHERE points = (SELECT MAX(points) FROM students)
Average points grouped by lastname
SELECT 
    last_name,
    AVG(points) average_points
FROM students
GROUP BY last_name
ORDER BY average_points DESC
Select all students with points greater than 70 (comparison operators: 
>
>=
<
<=
=
!=
<>
)
SELECT *
FROM students
WHERE points > 70
Select all students with points less than or equal to 70 (using NOT logical operator)
SELECT *
FROM students
WHERE NOT points > 70
Select all students with points between 80 and 90
SELECT *
FROM students
WHERE points >= 80
    AND points <= 90
Select all students with points between 80 and 90 (using BETWEEN AND operator)
SELECT *
FROM students
WHERE points BETWEEN 80 AND 90
Select all students with points more than average
SELECT *
FROM students
WHERE points > (SELECT AVG(points) FROM students)
Select all students where lastname is either 'გელაშვილი' or 'გოგუაძე' with 
IN
operator
SELECT *
FROM students
WHERE last_name IN ('გელაშვილი', 'გოგუაძე')
Select all students which lastname is not any of the listed lastnames ('გელაშვილი', 'გოგუაძე') with 
NOT IN
operator
SELECT *
FROM students
WHERE last_name NOT IN ('გელაშვილი', 'გოგუაძე')
Select all students which lastname contains 'უა' with 
LIKE
operator
SELECT *
FROM students
WHERE last_name LIKE '%უა%'
Select all students which 
lastname
ends with 'უა' using 
LIKE
operator
SELECT *
FROM students
WHERE last_name LIKE '%უა'
Select all students which 
lastname
does not contain 'უა' with 
NOT LIKE
operator
SELECT *
FROM students
WHERE last_name NOT LIKE '%უა%'
Select all students where 
lastname
starts with any two character followed with 
უა
and we don't care what the other following symbols are (with 
_
)
SELECT *
FROM students
WHERE last_name LIKE '__უა%'
Select all students where 
lastname
is exactly 5 characters long and the second symbol is 
უ
SELECT *
FROM students
WHERE last_name LIKE '_უ___'
Select all students where 
lastname
is exactly 5 characters, starts with 
a
and ends with 
y
and has exacly any three letters between them
SELECT *
FROM students
WHERE last_name LIKE 'a___y'
Select all students where 
lastname
ends with either 
ძე
or 
შვილი
SELECT *
FROM students
WHERE last_name LIKE '%ძე' OR last_name LIKE '%შვილი'
Select all students where 
last_name
contains 
უა
with 
REGEXP
operator
SELECT *
FROM students
WHERE last_name REGEXP 'უა'
Select all students where 
last_name
starts with 
გე
with 
REGEXP
operator
SELECT *
FROM students
WHERE last_name REGEXP '^გე'
Select all students where 
last_name
ends with 
უა
with 
REGEXP
operator
SELECT *
FROM students
WHERE last_name REGEXP 'უა$'
Select all students where 
last_name
contains 
უა
or 
ია
SELECT *
FROM students
WHERE last_name REGEXP 'უა|ია'
Select all students where 
last_name
contains 
უა
or 
ია
using square brackets 
SELECT *
FROM students
WHERE last_name REGEXP '[იუ]ა'
Select all students where 
last_name
ends with any one letter from the range 
[ა-უ]
followed by 
ა
using square brackets with range
SELECT *
FROM students
WHERE last_name REGEXP '[ა-უ]ა$'
Select all students where 
last_name
contains 
ვა
or ends with 
ია
or starts with 
ცი
SELECT *
FROM students
WHERE last_name REGEXP '^ცი|ია$|ვა'
Select all students which has no mail with 
IS NULL
operator
SELECT *
FROM students
WHERE mail IS NULL 
    OR mail = ''
Select all students which has no mail using 
IFNULL()
function
SELECT *
FROM students
WHERE IFNULL(mail, '') = ''
Select all students which has mail using 
IS NOT NULL
operator
SELECT *
FROM students
WHERE mail IS NOT NULL
    AND mail != ''
Select all students which has mail using 
NULLIF()
function
SELECT *
FROM students
WHERE NULLIF(mail, '') IS NOT NULL
Select notes with author names (using INNER JOIN)
SELECT students.first_name, notes.*
FROM `students` 
JOIN notes ON notes.student_id = students.id
Select notes with author names (from students using LEFT JOIN)
SELECT students.first_name, notes.*
FROM `students` 
LEFT JOIN notes ON notes.student_id = students.id
Select notes with author names (from students using RIGHT JOIN)
SELECT 
    students.first_name, 
    notes.*
FROM `notes` 
RIGHT JOIN students ON notes.student_id = students.id
Select notes with author names (from students using LEFT JOIN)
SELECT students.first_name, notes.*
FROM `students` 
LEFT JOIN notes ON notes.student_id = students.id
WHERE notes.id > 0
Select notes with author names (from notes)
SELECT students.first_name, notes.*
FROM `notes` 
LEFT JOIN students ON notes.student_id = students.id
WHERE notes.id > 0
Select only students with notes (using INNER JOIN)
SELECT students.*, COUNT(students.id) notes_count 
FROM `students` 
JOIN notes ON notes.student_id = students.id
GROUP BY students.id
ORDER BY notes_count DESC
Selects only students with notes (using LEFT JOIN and HAVING) 
SELECT students.*, COUNT(notes.id) notes_count 
FROM `students` 
LEFT JOIN notes ON notes.student_id = students.id
GROUP BY students.id
HAVING notes_count > 0
ORDER BY notes_count DESC
LIMIT 2
Select popular notes with its authors and likes counts
SELECT 
    students.first_name, 
    notes.id AS note_id, 
    notes.note, 
    COUNT(note_likes.id) AS likes_count
FROM `notes` 
JOIN students ON notes.student_id = students.id
LEFT JOIN note_likes ON note_likes.note_id = notes.id
GROUP BY notes.id
ORDER BY likes_count DESC
Select only liked notes
SELECT 
    students.first_name, 
    notes.id AS note_id, 
    notes.note, 
    COUNT(note_likes.id) AS likes_count
FROM `notes` 
JOIN students ON notes.student_id = students.id
JOIN note_likes ON note_likes.note_id = notes.id
GROUP BY notes.id
ORDER BY likes_count DESC
Select only liked notes (without JOIN keywords)
SELECT 
    students.first_name, 
    notes.id AS note_id, 
    notes.note, 
    COUNT(note_likes.id) AS likes_count
FROM `notes`, students, note_likes
WHERE notes.student_id = students.id
    AND note_likes.note_id = notes.id
GROUP BY notes.id
ORDER BY likes_count DESC
Select liked notes with likes counts and authors (using sub-query)
SELECT 
    students.first_name, 
    note_id, 
    notes.note,
    liked_notes.likes_count
FROM (  
    	SELECT 
            note_likes.note_id AS note_id,
            COUNT(note_likes.id) AS likes_count
        FROM note_likes
        GROUP BY note_likes.note_id
	) AS `liked_notes`
JOIN notes ON liked_notes.note_id = notes.id
JOIN students ON notes.student_id = students.id
ORDER BY likes_count DESC
error: The following untracked working tree files would be overwritten by merge
When trying to pull the latest commits, the error was
error: The following untracked working tree files would be overwritten by merge:
        app/Log.php
The solution that fixed the problem:
git add * 
git stash
git pull
Results: 1021