[erlang-questions] Erlang and MySQL: ODBC, Column type not supported

[Ingela Andin]

Hi!

The erlang odbc application supports {sql-varchars,  N} where N = 255
in your case. The return values
you get suggest that the odbc-driver you have returns an unexpected column type.

In the erlang odbc port program there is a switch that handles type
when describing a coloumn that if we take out
the handling code looks like this.

switch(sql_type) {
    case SQL_CHAR:	
    case SQL_VARCHAR:
    case SQL_WCHAR:
    case SQL_WVARCHAR:
    case SQL_NUMERIC:
    case SQL_DECIMAL:
    case SQL_INTEGER:
    case SQL_TINYINT:
    case SQL_SMALLINT:
    case SQL_REAL:
    case SQL_FLOAT:
    case SQL_DOUBLE:
    case SQL_BIT:
    case SQL_TYPE_DATE:
    case SQL_TYPE_TIME:
    case SQL_TYPE_TIMESTAMP:
    case SQL_BIGINT:
    case SQL_BINARY:
    case SQL_LONGVARCHAR:
    case SQL_VARBINARY:
    case SQL_LONGVARBINARY:
    case SQL_INTERVAL_MONTH:
    case SQL_INTERVAL_YEAR:
    case SQL_INTERVAL_DAY:
    case SQL_INTERVAL_MINUTE:
    case SQL_INTERVAL_HOUR_TO_SECOND:
    case SQL_INTERVAL_MINUTE_TO_SECOND:
    case SQL_UNKNOWN_TYPE:
    default: /* Will probably never happen */
	ei_x_encode_atom(&dynamic_buffer(state), "ODBC_UNSUPPORTED_TYPE");
	break;
    }


And you end up in the default clause which is very unexpected and the
root to your problem.  If  you can figur out
what your driver returns for the ODBC C-API function SQLDescribeCol we
could know if the driver is at fault or if the odbc-port program is.

Regards  Ingela Erlang/OTP team - Ericsson AB

2011/5/1 Hanfei Shen <qqshfox@REDACTED>:
> Dear all,
>
> I'm a newbie programming in erlang. When I used ODBC to connect to a
> MySQL database through Connector/ODBC (MyODBC), I got some error when
> calling odbc:sql_query(Conn, "SELECT * FROM action"):
>
> {error,"Column type not supported"}
>
> Then I call odbc:describe_table(Conn, "action"), it returned:
>
> {ok,[{"id",sql_integer},
>      {"code",'ODBC_UNSUPPORTED_TYPE'},
>      {"compliment_desc",'ODBC_UNSUPPORTED_TYPE'},
>      {"status_desc",'ODBC_UNSUPPORTED_TYPE'},
>      {"parameter",'ODBC_UNSUPPORTED_TYPE'},
>      {"cause",'ODBC_UNSUPPORTED_TYPE'},
>      {"disabled",sql_tinyint}]}
>
> And desc the table in mysql client:
> mysql> desc action;
> +-----------------+--------------+------+-----+---------+----------------+
> | Field           | Type         | Null | Key | Default | Extra          |
> +-----------------+--------------+------+-----+---------+----------------+
> | id              | int(11)      | NO   | PRI | NULL    | auto_increment |
> | code            | varchar(255) | NO   |     | NULL    |                |
> | compliment_desc | varchar(255) | NO   |     |         |                |
> | status_desc     | varchar(255) | NO   |     |         |                |
> | parameter       | varchar(255) | NO   |     |         |                |
> | cause           | varchar(255) | NO   | UNI |         |                |
> | disabled        | tinyint(1)   | NO   |     | 0       |                |
> +-----------------+--------------+------+-----+---------+----------------+
>
> It seems that Erlang ODBC driver does not support the mysql type
> varchar? How can I use the database without touching the db schema?
>
>
> Some details about the system env:
>
> $ uname -a
> Linux 2.6.36-gentoo-r8 #4 SMP Thu Apr 7 20:13:18 CST 2011 x86_64
> Intel(R) Core(TM)2 Duo CPU E7500 @ 2.93GHz GenuineIntel GNU/Linux
>
> $ erl
> Erlang R13B04 (erts-5.7.5) [source] [64-bit] [smp:2:2] [rq:2]
> [async-threads:0] [kernel-poll:false]
>
> $ emerge -vp erlang
> dev-lang/erlang-13.2.4  USE="doc kpoll odbc smp ssl -emacs -hipe -java
> -sctp -tk -wxwidgets"
>
> eshell> code:which(odbc).
> "/usr/lib64/erlang/lib/odbc-2.10.7/ebin/odbc.beam"
>
> $ mysql -V
> mysql  Ver 14.14 Distrib 5.1.51, for pc-linux-gnu (x86_64) using readline 5.1
>
> Server version: 5.1.51-log Gentoo Linux mysql-5.1.51
>
> $ emerge -vp myodbc
> dev-db/myodbc-5.1.6  USE="-debug -doc -qt4 -static"
>
>
> Any help will be greatly appreciated.  Thanks in advance.
> Sorry for my poor English, I'm not a native...
>
> Best,
>
> --
> Hanfei
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