I use Python to merge MBTiles files. Be sure to update the matadata table noting the min max zoom. They are just sqlite databases with a unique extension.
This example does not include data validation. I did not test this example -- as it is stripped down from where I batch process output from QGIS.
It is less problematic to use an IDE other than QGIS's python interface. Does not require anything specific to QGIS or PyQGIS.
import sqlite3 as sqlite
def processOneSource(srcDB, dstDB):
# create_index_sql = "CREATE UNIQUE INDEX tile_index on tiles (zoom_level, tile_column, tile_row);"
# dstDB.connection.execute(create_index_sql)
# the index forces an error if there is already a tile for the same zxy
sqlite_insert_blob_query = """ INSERT INTO tiles (zoom_level, tile_column, tile_row, tile_data) VALUES (?, ?, ?, ?)"""
tiles = srcDB.connection.execute('select zoom_level, tile_column, tile_row, tile_data from tiles;')
for t in tiles:
z = t[0]
x = t[1]
y = t[2]
data = t[3]
# example of how you might include exclude tiles
if not (z == 12 or z == 13 or z == 14 or z == 15 or z == 16):
continue
print(str((t[0], t[1], t[2])))
data_tuple = (t[0], t[1], t[2], t[3])
try:
dstDB.connection.execute(sqlite_insert_blob_query, data_tuple)
except Exception as e:
print(e)
dstDB.commit()
if __name__ == '__main__':
srcDB = sqlite.connect("path_to_yourfilename")
dstDB = sqlite.connect("path_to_yourfilename")
processOneSource(srcDB, dstDB)