private String[] parseJoins() {
		int startIndex = content.indexOf(WHERE) + WHERE.length();
		int endIndex = content.indexOf(GROUP_BY);
		String[] filters = content.substring(startIndex, endIndex).trim().split(AND);
		String join = "";
		for (String filter : filters) {
			filter = filter.trim();
			for (String op : OP) {
				if (filter.indexOf(op) > 0) {
					String[] vars = filter.split(op);
					boolean isJoin = true;
					for (String v : vars) {
						v = v.trim();
						isJoin &= isVariable(v);
					}
					if (isJoin) {
						join += filter + SPLIT_STRING + WHITE_SPACE;
					}
				}
			}
		}
		return converStringToArray(join.substring(0, join.length() - 2), SPLIT_STRING);
	}