I'm using Oracle 18c. I'm trying to determine elapsed time, but I get an error when I subtract two date variables in PL SQL. The following code works fine:
DECLARE
l_zero_date date;
l_current_date date;
l_elapsed_time date;
BEGIN
Execute Immediate 'ALTER SESSION set nls_timestamp_format = "DD-MM-YYYY HH24:MI:SS"';
l_zero_date := to_date('01-01-1900 00:00:00', 'DD-MM-YYYY HH24:MI:SS');
dbms_output.put_line('The value of l_zero_date is: ' || l_zero_date);
Select ls.duration Into l_current_date From LIT_STATS ls Where ls.prim_key = 1002;
dbms_output.put_line('The value of l_curr_date is: ' || l_current_date);
-- dbms_output.put_line('The elapsed time is: ' || l_current_date - l_zero_date);
END;
This produces the results:
The value of l_zero_date is: 1900-01-01 00:00:00
The value of l_curr_date is: 1900-01-01 00:35:22
However, If I un-comment the last dbms_output line I get the error:
Error report -
ORA-06502: PL/SQL: numeric or value error: character to number conversion error
ORA-06512: at line 14
06502. 00000 - "PL/SQL: numeric or value error%s"
*Cause: An arithmetic, numeric, string, conversion, or constraint error
occurred. For example, this error occurs if an attempt is made to
assign the value NULL to a variable declared NOT NULL, or if an
attempt is made to assign an integer larger than 99 to a variable
declared NUMBER(2).
*Action: Change the data, how it is manipulated, or how it is declared so
that values do not violate constraints.
I don't understand why I get the error on subtraction involving two fields declared as DATE. For example, the following code works fine:
declare
a date;
b date;
begin
a := sysdate;
dbms_lock.sleep(10); -- sleep about 10 seconds give or take
b := sysdate;
dbms_output.put_line( b-a || ' of a day has elapsed' );
dbms_output.put_line( (b-a)*24 || ' of an hour has elapsed' );
dbms_output.put_line( (b-a)*24*60 || ' of a minute has elapsed' );
dbms_output.put_line( (b-a)*24*60*60 || ' seconds has elapsed' );
end;
Why does the line dbms_output.put_line('The elapsed time is: ' || l_current_date - l_zero_date);
produce an error?
Thanks for looking at this.
CodePudding user response:
As I mentioned in the comments, this is an order of operations issue. Take the following example:
SELECT 'TEST'||SYSDATE-SYSDATE FROM DUAL
When this runs, I get the following error: ORA-00932: inconsistent datatypes: expected CHAR got DATE
But when I wrap the dates in (
and )
:
SELECT 'TEST'||(SYSDATE-SYSDATE) FROM DUAL
The result is TEST0
.
It is order of operations, the code moves left to right unless there are parentheses informing it to do the date subtraction first.
Here is a DBFiddle showing the queries being run (LINK)