SQLD(SQL 개발자) 기출 · NULL

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1. 1.select NVL(a.COL1,-1) as data from Mytest a;
2. 2.select DECODE(a.COL1, null,-1,a.col1) as data from Mytest a;
3. 3.select case when a.COL1 is null then -1 else 0 end as data from Mytest a;
4. 4.select case a.COL1 when null then -1 else 0 end as data from Mytest a;