code: function _join() {
      var sql = '',
          i = -1,
          joins = this.grouped.join;
      if (!joins) {
        return '';
      }
      while (++i < joins.length) {
        var join = joins[i];
        if (i > 0) {
          sql += ' ';
        }
        if (join.joinType === 'raw') {
          sql += this.formatter.unwrapRaw(join.table);
        } else {
          sql += join.joinType + ' join ' + this.formatter.wrap(join.table);
          var ii = -1;
          while (++ii < join.clauses.length) {
            var clause = join.clauses[ii];
            sql += ' ' + (ii > 0 ? clause[0] : clause[1]) + ' ';
            sql += this.formatter.wrap(clause[2]);
            if (clause[3]) {
              sql += ' ' + this.formatter.operator(clause[3]);
            }
            if (clause[4]) {
              sql += ' ' + this.formatter.wrap(clause[4]);
            }
          }
        }
      }
      return sql;
    }
docs: Compiles all each of the `join` clauses on the query, including any nested join queries.