==

(Equal) Returns true if $x is equal to $y

$x = 40; 
$y = "40";
var_dump($x == $y); // true

===

(Identical) Returns true if $x is equal to $y, and they are of the same type

$x = 40; 
$y = "40";
var_dump($x === $y); // false

!=

(Not equal) Returns true if $x is not equal to $y

$x = 40; 
$y = "40";
var_dump($x != $y); // false

<>

(Not equal) Returns true if $x is not equal to $y

$x = 40; 
$y = "40";
var_dump($x <> $y); // false

!==

(Not identical) Returns true if $x is not equal to $y, or they are not of the same type

$x = 40; 
$y = "40";
var_dump($x !== $y); // true

>

(Greater than) Returns true if $x is greater than $y

$x = 40; 
$y = 50;
var_dump($x > $y); // false

<

(Less than) Returns true if $x is less than $y

$x = 40; 
$y = 50;
var_dump($x < $y); // true

>=

(Greater than or equal to) Returns true if $x is greater than or equal to $y

$x = 40; 
$y = 50;
var_dump($x >= $y); // false

<=

(Less than or equal to) Returns true if $x is less than or equal to $y

$x = 40; 
$y = 50;
var_dump($x <= $y); // true

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";

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

0

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

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

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);

Creates

sdt_prices_unique

table with exactly the same structure as

sdt_prices

table has

CREATE TABLE sdt_prices_unique LIKE sdt_prices

Makes

columnname

column UNIQUE

ALTER TABLE dbname.tablename
ADD UNIQUE (columnname)

Inserts all rows, ignores rows with

Duplicate key

error

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

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;

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;