Oracle Update column based on an expression

I have a table which has a calculated VARCHAR2 column based on an event date. Yes, I know that this is not advisable.
age_group is a VARCHAR2 column.
start_date is a DATE column.

I need to set the value of the age_group  column.

Psuedocode: Set the value of Table1.age_group  equal to 'LT8'
where the number of days since the start date is between 0 and 7.

UPDATE Table1
SET age_group = ‘LT8’  
WHERE  Table1 .(SysDate-start_date)  BETWEEN 0 AND 7 ;

Is this the correct syntax?  Does (SysDate - start-date) return a number of days, or do I need to apply a conversion function?

Thanks,
DovbermanAsked:
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Haris DulicIT ArchitectCommented:
UPDATE Table1
SET age_group = ‘LT8’  
WHERE SysDate- to_Date(start_date,'yyyy-mm-dd')  BETWEEN 0 AND 7 ;

before you update first test the records affected by running :

select start_date, SysDate- to_Date(start_date,'yyyy-mm-dd')   as diff
from Table1

WHERE SysDate- to_Date(start_date,'yyyy-mm-dd')  BETWEEN 0 AND 7 ;
DovbermanAuthor Commented:
Thanks,

This is part of a procedure.
Will a count work? I need a count for each of 9 date different groups.

SELECT Count(start_date) as Group1 WHERE SysDate- to_Date(start_date,'yyyy-mm-dd')  BETWEEN 0 AND 7,
 SELECT Count(start_date) as Group2 WHERE SysDate- to_Date(start_date,'yyyy-mm-dd')  BETWEEN 8 AND 30 ;

Returns:
Group1       Group2    ...

Thanks,
27                56
Haris DulicIT ArchitectCommented:
try this, you just need to add additional case statements and sums

select suM(group1) as group1, sum(group2) as group2
from(
SELECT 
case when SysDate- to_Date(start_date,'yyyy-mm-dd')  BETWEEN 0 AND 7 then 1 else 0 end as group1,
case when SysDate- to_Date(start_date,'yyyy-mm-dd')   BETWEEN 8 AND 30 then 1 else 0 end as group2
from table1
)a

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DovbermanAuthor Commented:
Just what I was looking for.
Haris DulicIT ArchitectCommented:
Glad that I helped ;)
DovbermanAuthor Commented:
Just what I was looking for.

Thanks
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