code: public static String getSelectCountSQL(Class<?> clazz) {
  		StringBuilder sql = new StringBuilder();
  		sql.append("SELECT count(*)");
  		
  		// 处理join方式clazz
  		JoinTable joinTable = DOInfoReader.getJoinTable(clazz);
  		if(joinTable != null) {
  			Field leftTableField = DOInfoReader.getJoinLeftTable(clazz);
  			Field rightTableField = DOInfoReader.getJoinRightTable(clazz);
  			
  			JoinLeftTable joinLeftTable = leftTableField.getAnnotation(JoinLeftTable.class);
  			JoinRightTable joinRightTable = rightTableField.getAnnotation(JoinRightTable.class);
  			
  	        Table table1 = DOInfoReader.getTable(leftTableField.getType());
  	        Table table2 = DOInfoReader.getTable(rightTableField.getType());
  	        
  	        sql.append(" FROM ").append(getTableName(table1))
  	           .append(" ").append(joinLeftTable.alias()).append(" ");
  	        sql.append(joinTable.joinType().getCode()).append(" ");
  	        sql.append(getTableName(table2)).append(" ").append(joinRightTable.alias());
  	        if(joinTable.on() == null || joinTable.on().trim().isEmpty()) {
  	        	throw new OnConditionIsNeedException("join table VO:" + clazz.getName());
  	        }
  	        sql.append(" on ").append(joinTable.on().trim());
  	        
  		} else {
  			Table table = DOInfoReader.getTable(clazz);
  			sql.append(" FROM ").append(getTableName(table));
  		}
  		
  		return sql.toString();
  	}
docs: select count(*) from t_table, 不包含where子句及以后的语句
  @param clazz
  @return