| MiniOB 1
    MiniOB is one mini database, helping developers to learn how database works. | 
成员的完整列表,这些成员属于 Stmt,包括所有继承而来的类成员
| create_stmt(Db *db, ParsedSqlNode &sql_node, Stmt *&stmt) (定义于 Stmt) | Stmt | static | 
| Stmt()=default (定义于 Stmt) | Stmt | |
| type() const =0 (定义于 Stmt) | Stmt | pure virtual | 
| ~Stmt()=default (定义于 Stmt) | Stmt | virtual |