Oracle NVL即使使用不为空也无法处理空字符串

Question

I am trying to return empty or dummy string if select query returns null .I tried using dummy value in NVL(colum,'dummy') , but I am still getting no data found error. Below is what I tried:

1.

  SELECT de.destination INTO l_sub_ent

  FROM dest de

  where de.destination='somevalue' AND de.destination IS NOT NULL; 

2.

  SELECT COALSECE(de.destination, 'dummy') INTO l_sub_ent

  FROM dest de

  where de.destination ='some value'; 

3.

  SELECT NVL(de.desc_en, 'dummy') INTO l_sub_ent

  FROM dest de

  where de.destination ='some value'; 

Answer 1

Problem is not that your de.destination is NULL . There are no records for the condition de.destination='somevalue' . Handle it something like this.

SELECT Count(1)
INTO   v_count
FROM   dest de
WHERE  de.destination='somevalue';

IF v_count > 0 THEN
  SELECT NVL(de.destination,'dummy')
  INTO   l_sub_ent
  FROM   dest de
  WHERE  de.destination='somevalue';
END IF; 

Answer 2

I was able to solve using below :

SELECT NVL(MIN(val), 'dummy') INTO l_sub_ent

  FROM dest de

  where de.destination ='some value';