MySQL 准备好的语句不返回结果 java

Question

i have a simple stored procedure in mysql and am trying to call it from jdbc. i keep getting an empty result set. i've searched and tried several solutions on similar threads to no avail. note that table.quantity is not a fixed decimal, which is why i'm using double/BigDecimal.

the relevant columns in my table are:

quantity   DOUBLE UNSIGNED
orderTime  TIMESTAMP

and here is the stored procedure:

CREATE DEFINER=`root`@`localhost` PROCEDURE `getTotal`( IN pSince TIMESTAMP, OUT pVolume DOUBLE UNSIGNED )
BEGIN
    SET pVolume = ( SELECT SUM( quantity ) FROM db.table WHERE orderTime > pSince );
END

i've also tried it like this:

BEGIN
    SELECT SUM( quantity ) INTO pVolume FROM db.table WHERE orderTime > pSince;
END

neither seems to work when i call it like this:

CallableStatement lCall = getConnection().prepareCall( "{call getTotal(?,?)}" );
lCall.setTimestamp( 1, new Timestamp( System.currentTimeMillis() - 600000 ));
lCall.registerOutParameter( 2, Types.DOUBLE );
lCall.execute();
ResultSet lResults = lCall.getResultSet();
lResults.next();
return lResults.getBigDecimal( 1 );

this returns an empty result set.

adding lResults.beforeFirst() throws a null pointer exception because the lResults.rowData is null. i've also tried lResults.getBigDecimal( "pVolume" ) with the same result.

i've also tried:

ResultSet lResults = lCall.executeQuery();
lResults.next();
return lResults.getBigDecimal( 1 );

which throws a SQLException on lResults.next() because it says the call was an UPDATE and, therefore, doesn't have any results.

i suspect that i'm missing something in my stored procedure. any ideas?? oh, and i'm logging in as dev, not root. i checked the permissions and i can execute.

Answer 1

Results from CallableStatement are retrieved directly through its (own) declared methods:

lCall.execute();
return lCall.getBigDecimal( 2 );
// do not forget to close the statement - try-with-resource

no need to call getResultSet() (from Statement ).

Documentation :

The type of all OUT parameters must be registered prior to executing the stored procedure; their values are retrieved after execution via the get methods provided here .