Delete zoom levels from an MBTiles file (set max zoom)

mbtiles_delete_zoom_level.sql

-- change 18 to whatever the max zoom level you want in your MBTiles

DELETE FROM images WHERE 
  tile_id IN (SELECT tile_id FROM map WHERE zoom_level > 18) AND
  tile_id NOT IN (SELECT tile_id FROM map WHERE zoom_level <= 18);

DELETE FROM map WHERE zoom_level > 18;

UPDATE metadata SET value = '18' WHERE name = 'maxzoom';

-- now run the VACUUM command

DELETE FROM tiles_data WHERE 
  tile_data_id IN (SELECT tile_data_id FROM tiles_shallow WHERE zoom_level > 9) AND
  tile_data_id NOT IN (SELECT tile_data_id FROM tiles_shallow WHERE zoom_level <= 9);

DELETE FROM tiles_shallow WHERE zoom_level > 9;

UPDATE metadata SET value = '9' WHERE name = 'maxzoom';

VACUUM;