c++ mysql存储前过程多个输出参数错误

Question

我使用 Freebsd 8.0 amd64、mysql-client-5.1.61、mysql-connector-c++-1.1.0、mysql-server-5.1.61 和 gcc 4.2.1 Whay 这是有效的

stmt->execute("CREATE PROCEDURE p(OUT retval VARCHAR(50)) BEGIN SELECT \"Ulf joined MySQL more than 5 years ago\" INTO retval; END;");

 pstmt.reset(con->prepareStatement("CALL p(@output)"));
 pstmt->execute();

 pstmt.reset(con->prepareStatement("SELECT @output AS _answer"));
 res.reset(pstmt->executeQuery());
 while (res->next())
     cout << "\t... _answer: " << res->getString("_answer") << endl;

这不是

stmt->execute("CREATE PROCEDURE p(OUT retval VARCHAR(50),OUT retval1 VARCHAR(50)) BEGIN SELECT \"Ulf joined MySQL more than 5 years ago\" INTO retval;SELECT \"Ulf joined MySQL more than 5 years ago\" INTO retval1;  END;");
pstmt.reset(con->prepareStatement("CALL p(@out1,@out2)"));
pstmt->execute();

pstmt.reset(con->prepareStatement("SELECT @out1 AS vOut,@out2 as vOut2"));
res.reset(pstmt->executeQuery());
while (res->next())
   cout << res->getString("vOut1") << res->getString("vOut2") << endl;

并返回 ERR: MySQLPreparedResultSet::getString: invalid 'columnIndex' (MySQL error code: 0, SQLState: )怎么了？

Answer 1

假设您逐字复制了代码，我认为问题是由一个简单的拼写错误引起的。在这一行中:

pstmt.reset(con->prepareStatement("SELECT @out1 AS vOut,@out2 as vOut2"));

参数的列名是 vOut 和 vOut2。但在后一行:

cout << res->getString("vOut1") << res->getString("vOut2") << endl;

您将它们称为 vOut1 和 vOut2。没有名称为 vOut1 的列，因为您将其命名为 vOut，因此列索引错误无效。