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Oracle SQL decode ??????????

decode ???????

? Oracle SQL ??decode ??????????????????????????????

decode( string , number , string1 , string2 , ... , stringN )

???string ???????????? string1?string2 ????????????????????????decode ?????????????????????? NULL ????????

IF-THEN-ELSE ????

???????decode ???? IF-THEN-ELSE ???????????????????????????????????

IF condition THEN    RETURN ( value_1 )ELSIF condition_2 THEN    RETURN ( value_2 )...ELSIF condition_n THEN    RETURN ( value_n )ELSE    RETURN ( default_value )END IF

???

IF "select column from table" = 'X' THEN    RETURN (1)ELSIF "select column from table" = 'Y' THEN    RETURN (2)ELSE    RETURN (0)END IF

????????????????????????????

LPAD ?????

?? decode ???LPAD??????????????????????????????????????????????????

LPAD( decode("direction", 1, 'N', 'S'), 14, '0' )

?? direction ????? 'N'?? decode ????? 1???? LPAD ?????????? 14 ??????? '0000000000000001'?

??????

?? 1????????

select LPAD(decode(count( directory ), 0, 1, max( to_number( directory ) + 1 )), 14, '0') from tetdmis

?????????????? decode ??????????LPAD ???????? 14 ????????? '0'?

?? 2?????

select decode( "subject_name", 'A', 1, 'B', 2, 'C', 3 ) from table_subject

?????? subject_name ?????????? 1?2 ? 3?????????????????

?? 3??????????

IF "column" = 'X' THEN    RETURN (1)ELSE    RETURN (0)END IF

???decode ??????????? SIGN ?????

sign( decode("column1", 10, "column2", 20) - 1 )

?????????????????????????????????

??????

????????????????????

???????Oracle SQL decode ?????????????????????????????????