M2 - Delete Gallery Image Where Not like sku.jpg or Seconday Image.

delete-gal-img.sql

DELETE
  galval,
  gal
FROM
  catalog_product_entity_media_gallery_value galval
  JOIN catalog_product_entity_media_gallery gal
    ON galval.value_id = gal.value_id
WHERE galval.value_id IN
  (SELECT
    value_id
  FROM
    (SELECT
      galval.value_id AS value_id
    FROM
      catalog_product_entity cpe
      LEFT JOIN catalog_product_entity_varchar AS image
        ON cpe.row_id = image.row_id
        AND image.attribute_id = 87 #image
         AND image.store_id = 0
      LEFT JOIN catalog_product_entity_media_gallery_value AS galval
        ON (cpe.row_id = galval.row_id)
      LEFT JOIN catalog_product_entity_media_gallery AS gal
        ON (galval.value_id = gal.value_id)
    WHERE image.value LIKE CONCAT(
        '%',
        TRIM('-1' FROM SUBSTRING(cpe.sku, 4)),
        '%'
      ) # where image like sku with or without last "-1" as many images don't have it
       AND gal.value NOT LIKE CONCAT(
        '%',
        TRIM('-1' FROM SUBSTRING(cpe.sku, 4)),
        '%'
      ) # where gallery image like sku with or without last "-1" as many images don't have it
       AND gal.value NOT REGEXP 'a[0-9].jpg' #not a secondary image a1, a2 etc)
    ) value_ids)