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Applications.ge
Modules
- Basics of Programming
- Problem Solving
- Git
- HTML
- CSS
- Sass
- JavaScript
- PHP
- Laravel
Meetings
Challenges
Projects
Tutorials
Channels
Notes
Resources

Results: 1580

Notes

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Disable / enable foreign key checks

First we disable

FOREIGN_KEY_CHECKS

to be able to run queries, then we enable

FOREIGN_KEY_CHECKS

back

SET FOREIGN_KEY_CHECKS=0;
--- Runs some SQL query - for example deleting some rows from a table that has foreign keys
SET FOREIGN_KEY_CHECKS=1;

by Valeri Tandilashvili

MySQL

Lost connection to MySQL server during query

When trying to import database the following problem occurred:

ERROR 2013 (HY000) at line 430: Lost connection to MySQL server during query

Solution to the problem was to increase connection timeout variable by running to following query:

SET GLOBAL connect_timeout = 10;

by Valeri Tandilashvili

MySQL

INSERT IGNORE INTO

Inserts all rows, ignores rows with

Duplicate key

error

INSERT IGNORE INTO dbname.prices_unique
SELECT * FROM dbname.prices

by Valeri Tandilashvili

MySQL

Make existing column UNIQUE

Makes

columnname

column UNIQUE

ALTER TABLE dbname.tablename
ADD UNIQUE (columnname)

by Valeri Tandilashvili

MySQL

CREATE TABLE LIKE

Creates

sdt_prices_unique

table with exactly the same structure as

sdt_prices

table has

CREATE TABLE sdt_prices_unique LIKE sdt_prices

by Valeri Tandilashvili

MySQL

UNIQUE several columns combined

Columns

token_id

and

base_price_pair

combined will be in the table

ALTER TABLE sdtokens.sdt_prices_unique
ADD UNIQUE (token_id, base_price_pair);

by Valeri Tandilashvili

MySQL

javascript array unique values

Make javascript array unique

var arr = [55, 44, 65,1,2,3,3,34,5];
var unique = [...new Set(arr)]

by Luka Tatarishvili

JavaScript

array

Show table sizes

Shows all the tables with their sizes in MB with descending order

SELECT 
    table_name AS `Table`, 
    round(((data_length + index_length) / 1024 / 1024), 2) AS MB_size 
FROM information_schema.TABLES 
WHERE table_schema = "database_name"
order by MB_size desc

by Valeri Tandilashvili

MySQL

Comparing two double numbers

The following code executes the

else

statement because the

float

numbers are different

if (strval(0.000000000035436064) == strval(0.000000000035436064000001)) {
    echo 'if';
} else {
    echo 'else';
}

But if we add one

in front of the last digit of the second number, then

if

statement will be executed

if (strval(0.000000000035436064) == strval(0.0000000000354360640000001)) {
    echo 'if';
} else {
    echo 'else';
}

Note:

The above code is one of the best solutions to compare float numbers

by Valeri Tandilashvili

PHP

Assignment Operators CODE

Assignment operators are used with:

integer

and

float

values to write / update a variable value. Simple Assignment

$y = 9;
$x = $y;
echo $x . "\n";

Addition

$x = 40; $y = 9;
$x += $y; // same as: $x = $x + $y
echo $x . "\n";

Subtraction

$x = 40; $y = 9;
$x -= $y; // $x = $x - $y
echo $x . "\n";

Multiplication

$x = 40; $y = 9;
$x *= $y; // $x = $x * $y
echo $x . "\n";

Division

$x = 40; $y = 9;
$x /= $y; // $x = $x / $y
echo $x . "\n";

Modulus

$x = 40; $y = 9;
$x %= $y; // $x = $x % $y
echo $x . "\n";

by Valeri Tandilashvili

PHP

Results: 1580