help with next_day

You do not need to use to_char:

select NEXT_DAY(to_date(20131003,'yyyymmdd'),'Tuesday') from dual;

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Try

select NEXT_DAY(to_date('20131003','yyyymmdd'),'Tuesday') from dual;

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and read
http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions093.htm

Do you want the next 'Tuesday' from the date you are entering? You're entering 20131003, the next Tuesday would be 20131008, is that what you want?

This will get you the next Tuesday in YYYYMMDD format from the given date:

select to_char(next_day(to_date('20131003','YYYYMMDD'),'Tuesday'),'YYYYMMDD') NEXT_TUESDAY from dual;

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This will get you the next Tuesday from today (sysdate):

select to_char(next_day(sysdate,'Tuesday'),'YYYYMMDD') NEXT_TUESDAY from dual;

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I am trying to use this within a case statement, when i use it standalone from dual it's fine, but when i u do

CASE WHEN substr(RVCCUSWK1,1,1) = 1 THEN to_char(next_day(sysdate,'Sunday'),'YYYYMMDD') ELSE 0 END AS SUN, 

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I get

ORA-00932: inconsistent datatypes: expected CHAR got NUMBER
00932. 00000 -  "inconsistent datatypes: expected %s got %s"
*Cause:    
*Action:
Error at Line: 15 Column: 97

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