Update Failed for Sum of previous row and current row

Question

Hi i need to update the column length of the previous row and current row so i followed this method but i'm unable to update what is problem in my syntax
SQL> begin
2 DECLARE Total number = 0;
3 UPDATE StringOutput set Total = SumOfLength = Total + ColLength;
4 end;
5 /
DECLARE Total number = 0;
ERROR at line 2:
ORA-06550: line 2, column 22:
PLS-00103: Encountered the symbol "=" when expecting one of the following:
:= . ( @ % ; not null range default character
if i update without the variable total then my command is succeeded
UPDATE StringOutput set SumOfLength = ColLength;
but i need the previous row+current row count in SumOfLength
Thanks!

Answer 1

Getting this error now
SQL> begin
2 DECLARE Total number := 0;
3 UPDATE StringOutput set Total = SumOfLength = Total + ColLength;
4 end;
5 /
UPDATE StringOutput set Total = SumOfLength = Total + ColLength;
ERROR at line 3:
ORA-06550: line 3, column 1:
PLS-00103: Encountered the symbol "UPDATE" when expecting one of the following:
begin function pragma procedure subtype type <an identifier>
<a double-quoted delimited-identifier> current cursor delete
exists prior
The symbol "begin" was substituted for "UPDATE" to continue.
ORA-06550: line 3, column 46:
PLS-00103: Encountered the symbol "=" when expecting one of the following:
. ( , * @ % & - + ; / at mod remainder rem return returning
<an exponent (**)> where || multiset
The symbol ". was inserted before "=" to continue.
ORA-06550: line 4, column 4:
PLS-00103: Encountered the symbol "end-of-file" when expecting one of the
following:
( begin case declare end exception exit for goto if loop mod
null pragma raise return select update while with
<an identifier> <a double-quoted