DB-cleanup.sql

DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_meta-robots' AND meta_value = 'index,follow';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_meta-robots-noindex' AND meta_value = '0';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_meta-robots-nofollow' AND meta_value = '0';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_meta-robots-adv' AND meta_value = 'none';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_meta-robots-adv' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_sitemap-prio' AND meta_value = '-';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_sitemap-include' AND meta_value = '-';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_opengraph-description' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_google-plus-description' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_title' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_metadesc' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_metakeywords' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_focuskw' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_bctitle' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_canonical' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_redirect' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_wpseo_video_meta' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_video_meta' AND meta_value = 'none';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_linkdex' AND meta_value = '0';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_newssitemap-original' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_newssitemap-stocktickers' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_sitemap-html-include' AND meta_value = '-';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_opengraph-image' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_videositemap-tags' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_videositemap-category' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_videositemap-rating' AND meta_value = '';
DELETE FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_videositemap-thumbnail' AND meta_value = '';

If you want to see what the value are first as well as how many there are, before deleting them:

SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_meta-robots' AND meta_value = 'index,follow'
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_meta-robots-noindex' AND meta_value = '0'
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_meta-robots-nofollow' AND meta_value = '0'
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_meta-robots-adv' AND meta_value = 'none'
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_meta-robots-adv' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_sitemap-prio' AND meta_value = '-'
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_sitemap-include' AND meta_value = '-'
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_opengraph-description' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_google-plus-description' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_title' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_metadesc' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_metakeywords' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_focuskw' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_bctitle' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_canonical' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_redirect' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_wpseo_video_meta' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_video_meta' AND meta_value = 'none'
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_linkdex' AND meta_value = '0'
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_newssitemap-original' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_newssitemap-stocktickers' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_sitemap-html-include' AND meta_value = '-'
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_opengraph-image' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_videositemap-tags' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_videositemap-category' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_videositemap-rating' AND meta_value = ''
UNION
SELECT * FROM wp_postmeta WHERE meta_key = '_yoast_wpseo_videositemap-thumbnail' AND meta_value = ''

Hi,
That's what I need but using it, it crash my WPML plugin, maybe there's an updated script?
Thanks

Is it safe to delete all the _yoast_wpseo_metakeywords records, now that this feature is no longer supported?
Even when the value is not empty?