Oracle DBAÅàѵ£ºÍ¨Óõ¥Ðк¯Êý

NVL()º¯Êý

select nvl(comm,0) from emp;

NULLIF()º¯Êý

Èç¹û±í´ïʽ exp1 Óë exp2 µÄÖµÏàµÈÔò·µ»Ø null£¬·ñÔò ·µ»Ø exp1 µÄÖµ

NVL2()º¯Êý

select empno, ename, sal, comm, nvl2(comm, sal+comm, sal) total from emp;

COALESCE()º¯Êý

ÒÀ´Î¿¼²ì¸÷²ÎÊý±í´ïʽ£¬Óöµ½·Ç null Öµ¼´Í£Ö¹²¢·µ »Ø¸ÃÖµ¡£

select empno, ename, sal, comm, coalesce(sal+comm, sal, 0)×ÜÊÕÈë from emp;

CASE ±í´ïʽ

select empno, ename, sal, case deptno

when 10 then '²ÆÎñ²¿'

when 20 then 'Ñз¢²¿' when 30 then 'ÏúÊÛ²¿' else 'δ֪²¿ÃÅ'

end ²¿ÃÅ

from emp;

DECODE()º¯Êý

ºÍ case ±í´ïʽÀàËÆ£¬decode()º¯ÊýÒ²ÓÃÓÚʵÏֶ෷ÖÖ§½á¹¹

select empno, ename, sal, decode(deptno, 10, '²ÆÎñ²¿',

20, 'Ñз¢²¿',

30, 'ÏúÊÛ²¿',

'δ֪²¿ÃÅ')²¿ÃÅ

from emp;