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? Oracle SQL ??decode ??????????????????????????????
decode( string , number , string1 , string2 , ... , stringN )
???string ???????????? string1?string2 ????????????????????????decode ?????????????????????? NULL ????????
???????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
????????????????????????????
?? decode ???LPAD??????????????????????????????????????????????????
LPAD( decode("direction", 1, 'N', 'S'), 14, '0' ) ?? direction ????? 'N'?? decode ????? 1???? LPAD ?????????? 14 ??????? '0000000000000001'?
select LPAD(decode(count( directory ), 0, 1, max( to_number( directory ) + 1 )), 14, '0') from tetdmis
?????????????? decode ??????????LPAD ???????? 14 ????????? '0'?
select decode( "subject_name", 'A', 1, 'B', 2, 'C', 3 ) from table_subject
?????? subject_name ?????????? 1?2 ? 3?????????????????
IF "column" = 'X' THEN RETURN (1)ELSE RETURN (0)END IF
???decode ??????????? SIGN ?????
sign( decode("column1", 10, "column2", 20) - 1 ) ?????????????????????????????????
????????????????????
???????Oracle SQL decode ?????????????????????????????????
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