can you have more than one primary key code example
Example 1: how to make multiple keys as primary in bdms
CREATE TABLE `Donor`(
`did` int(50) NOT NULL,
`oid` int(50) NOT NULL,
`dname` varchar(50) NOT NULL,
`dblood` varchar(50) NOT NULL,
PRIMARY KEY (`did`, `oid`)
);
Example 2: sql primary key
SELECT cols.table_name, cols.column_name, cols.position, cons.status, cons.owner
FROM all_constraints cons, all_cons_columns cols
WHERE cols.table_name = 'CUSTOMERS'
AND cons.constraint_type = 'P'
AND cons.constraint_name = cols.constraint_name
AND cons.owner = cols.owner;
SELECT cols.table_name, cols.column_name, cols.position, cons.status, cons.owner
FROM all_constraints cons, all_cons_columns cols
WHERE cols.table_name = '<table-name>'
AND cons.constraint_type = 'P'
AND cons.constraint_name = cols.constraint_name
AND cons.owner = cols.owner;