Variable Table Name MySQL Stored Function

问题

I have several MySQL tables that maintains a tree structure of records. Each record have an ID and a Parent field. I want to write a stored function to get the parent ID, given a record ID.

The following is my first attempt, and it's incorrect. My problem is I do not know how to use variable table name.

delimiter $$

create function parent(
    tableName varchar(15),
    nodeId    int
) returns int
begin
    declare p int;
    select parent into p from tableName where id=nodeId;
    return p;
end$$

Please help. Thanks!

回答1:

After some research, apparently a stored function will not work in this case due to the fact stored functions cannot execute dynamic SQL. I change my implementation to a stored procedure.

delimiter $$

create procedure parent(tableName varchar(15), nodeId int)
begin
    set @s := concat('select parent from ', tableName, ' where id =', nodeId);
    prepare query from @s;
    execute query;
    deallocate prepare query;
end$$

delimiter ;

来源：https://stackoverflow.com/questions/22003322/variable-table-name-mysql-stored-function