SQLD 벼락치기 2부 · 08 Q14

QUESTION14

NULL 함수

아래 SQL의 실행 결과와 동일한 것은?

제시 SQL

SELECT COL1,
       CASE
         WHEN COL1 = '01' THEN NULL
         ELSE COL1
       END AS R1
FROM TAB;

①SELECT COL1, NULLIF(COL1, '01') AS R1 FROM TAB;
②SELECT COL1, NVL(COL1, '01') AS R1 FROM TAB;
③SELECT COL1, NVL(NULLIF(COL1,'01'), COL1) AS R1 FROM TAB;
④SELECT COL1, CASE WHEN COL1 IS NULL THEN '01' ELSE COL1 END AS R1 FROM TAB;