Move fists image inside pages on a custom field

I would like to make a sql command to move the first image found in a custom post=page in a custom_field=first image

Example before:

Page has in post_content

<img class=”alignleft size-full wp-image-757″ title=”Lorem ipsum” src=”https://localhost/images/2015/07/lorem-ipsum.jpg&#8221; alt=”” width=”150″ height=”214″ />Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

After sql command to remain just the text

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

An create an custom field named “first_image” that contain image link “https://localhost/images/2015/07/lorem-ipsum.jpg&#8221;