函数从查询中获取第一条记录并返回单个值

Posted 2021-02-27

Nothing amazing here, just an efficient way to get the first row.

Be sure to set your ORDER BY clause properly.

-- Person may have multiple addresses.  Gets FIRST record only
CREATE OR REPLACE FUNCTION get_first_address(person_id_in IN VARCHAR2) RETURN VARCHAR2 IS
    ret_value VARCHAR2(1024) := ' ';
 
    CURSOR the_cur(l_person VARCHAR2) IS
        SELECT street1 || ', ' || street2 
          FROM address 
         WHERE person_id = l_person
        ORDER BY date_added;
BEGIN
    OPEN the_cur(l_person);
 
    FETCH the_cur
        INTO ret_value;
 
    CLOSE the_cur;
 
    RETURN ret_value;
EXCEPTION
    WHEN NO_DATA_FOUND THEN
        RETURN ret_value;
    WHEN OTHERS THEN
        DBMS_OUTPUT.PUT_LINE('EXCEPTION IN get_first_address - ' || SQLCODE || ': ' || SQLERRM);
        RETURN ret_value;
END get_first_address;