How to change attribute dropdown type to multi-select in Magento 2?

Short Answer:

Not possible via Magento2 Admin Backend.

Solution:

You need to update eav_attribute table and edit information about backend_source, frontend_input etc.

Simple query for that is:

UPDATE `eav_attribute` SET `backend_model`="Magento\\Eav\\Model\\Entity\\Attribute\\Backend\\ArrayBackend", `backend_type`="varchar", `frontend_input`="multiselect", `source_model`=NULL WHERE `attribute_id`=YOUR_ATTRIBUTE_ID_INTEGER LIMIT 1

Replace YOUR_ATTRIBUTE_ID_INTEGER with your attribute_id like 355

Reference:

https://stackoverflow.com/a/57701845/2229148

How to disable products in Magento2 which dont have any gallery image?

UPDATE `catalog_product_entity_int` SET `value`=2 where `entity_id` in (SELECT a.`entity_id` FROM `catalog_product_entity` AS a LEFT JOIN `catalog_product_entity_media_gallery_value` AS b ON a.entity_id = b.entity_id LEFT JOIN `catalog_product_entity_media_gallery` AS c ON b.value_id = c.value_id WHERE c.value IS NULL) and `attribute_id` = 96

It is SQL query

Assumption:

value=2 means disable and value=1 means enable

attribute_id=96 means “status” attribute

References:

https://gist.github.com/tegansnyder/8464261#gistcomment-2910808

https://magento.stackexchange.com/a/83033/32283

How to batch edit multiple images to make square sized pictures with original image in center using php imagejpeg?

<?php
// WORKS FOR JPEG IMAGES ONLY. FOR PNG, change function names
// also create a folder named "out" in the $datadir folder
///only 4 lines to be edited
//1. dir in which your image files are present
$datadir="J:/dgcert/";
//2. Expected min. Width of the output file
$_outw=840;
//3. Expected min. Height of the output file
$_outh=840;
//4. output folder (inside datadir)
$outfolder= '/out/';
//5. force final size -- -- If set to 1/true then line 2 and 3 will become max sizes of output image
// TO BE DONE IN FUTURE . does not work as of now
$forcesize=0;
////// no more edits needed
$files=array_diff(scandir($datadir),array(".",".."));
foreach ($files as $file)
{
	if(is_file($datadir.'/'.$file)){		
$outw=$_outw;
$outh=$_outh;
$mugl_im= imagecreatefromjpeg($datadir.$file);
list($thiswidth, $thisheight)= getimagesize($datadir.$file);
if($outw<$thiswidth) $outw=$thiswidth;
if($outh<$thisheight) $outh=$thisheight;
if($outw<$outh)$outw=$outh;
if($outh<$outw)$outh=$outw;
//echo $width . $height;exit;
$thumb = imagecreatetruecolor($outw, $outh);
//white color rgb
$bg = imagecolorallocate ( $thumb, 255, 255, 255 );
imagefilledrectangle($thumb,0,0,$outw,$outh,$bg);
imagecopyresized($thumb,$mugl_im,ceil(($outw-$thiswidth)/2),ceil(($outh-$thisheight)/2),0,0,$thiswidth,$thisheight,$thiswidth,$thisheight);

imagejpeg($thumb,$datadir.$outfolder.$file);
imagedestroy($thumb);
imagedestroy($mugl_im);
	}
}

?>

How to wipe all the tables and data in MySQL? Clean whole database

SET FOREIGN_KEY_CHECKS = 0;
SET GROUP_CONCAT_MAX_LEN=32768;
SET @tables = NULL;
SELECT GROUP_CONCAT('`', table_name, '`') INTO @tables
  FROM information_schema.tables
  WHERE table_schema = (SELECT DATABASE());
SELECT IFNULL(@tables,'dummy') INTO @tables;
 
SET @tables = CONCAT('DROP TABLE IF EXISTS ', @tables);
PREPARE stmt FROM @tables;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
SET FOREIGN_KEY_CHECKS = 1;

Will not work via phpmyadmin or any script. this has to be run in cmd/terminal

Quick Command

wget https://gist.githubusercontent.com/harshvardhanmalpani/e670a8de7aa81673364dd48f125cb9ac/raw/ce04b319bf1594d148d3346e1474119fe1cd1b3f/flushdb.sql

mysql -hYOUR_DATABASE_HOSTNAME -uYOUR_DATABASE_USER -p YOUR_DATABASE_NAME < flushdb.sql

Source:
https://gist.github.com/harshvardhanmalpani/e670a8de7aa81673364dd48f125cb9ac