code: public ShardingStrategy getDatabaseShardingStrategy(final TableRule tableRule) {
          return null == tableRule.getDatabaseShardingStrategy() ? defaultDatabaseShardingStrategy : tableRule.getDatabaseShardingStrategy();
      }
docs: Get database sharding strategy.
  
  <p>
  Use default database sharding strategy if not found.
  </p>
  
  @param tableRule table rule
  @return database sharding strategy