What is the equivalent of Oracle’s REF CURSOR in M

问题:

In Oracle I can declare a reference cursor...

TYPE t_spool IS REF CURSOR RETURN spool%ROWTYPE;

...and use it to pass a cursor as the return value...

FUNCTION end_spool
    RETURN t_spool
    AS
    v_spool t_spool;
    BEGIN
        COMMIT;
        OPEN v_spool FOR
            SELECT
                *
            FROM
                spool
            WHERE
                key = g_spool_key
            ORDER BY
                seq;
        RETURN v_spool;
    END end_spool;

...and then capture it as a result set using JDBC...

private Connection conn;
private CallableStatement stmt;
private OracleResultSet rset;
[...clip...]
stmt = conn.prepareCall("{ ? = call " + call + "}");
stmt.registerOutParameter(1, OracleTypes.CURSOR);
stmt.execute();
rset = (OracleResultSet)stmt.getObject(1);

What is the equivalent in MySQL?

回答1:

Mysql has an implicit cursor that you can magically return from a stored procedure if you issue a select.

Here's an example:

CREATE PROCEDURE `TEST`()
MODIFIES SQL DATA
BEGIN
  SELECT * FROM test_table;
END;

and in your java code:

String query = "{CALL TEST()}";
CallableStatement cs = con.prepareCall(query,
    ResultSet.TYPE_SCROLL_INSENSITIVE,
    ResultSet.CONCUR_READ_ONLY);
ResultSet rs = cs.executeQuery();

回答2:

Googling on cursors in MySQL, it doesn't seem like you can actually return a Cursor from a Proc or Function. Additionally, I found the following in the MySQL JDBC manual:

"MySQL does not support SQL cursors, and the JDBC driver doesn't emulate them, so "setCursorName()" has no effect."

In general, I believe Oracle's implementation here breaks JDBC, and is not used elsewhere (MySQL, MSSQL, etc). You should be returning your results as a select statement and iterating over the JDBC ResultSet, as is standard (and intended) practice when using JDBC.

回答3:

fill a temporary table in a procedure and just read the temporary table... :)