Comparing date and timestamp variables in a where clause in a procedure

date formatoracleoracle-11g-r2timestamp

I have a variable in an Oracle stored procedure of DATE type (from user interface), and another of TIMESTAMP type (database is more precise than what the user would enter in the code that is executing the stored procedure).

I would like to do something like this: (pseudo code)

select * from MYDATABASE where inputDate = extract(date from myDatabaseTimeStamp);

but I get a compile error when I try this. Any idea what is a good actual code solution for this?

Best Answer

Assuming the DATE from user interface can contain times besides 00:00:00 (midnight) and that you only want to know if the DATE from the user interface and the TIMESTAMP fall on the same day (not same hour or minute or ?), try this:

...

myDatabaseDate    DATE;
myDatabaseNextDay DATE;

BEGIN

  -- Change TIMESTAMP to a DATE type with CAST, then TRUNCate time to 00:00:00.
  myDatabaseDate    := TRUNC( CAST(myDatabaseTimeStamp as DATE) );
  myDatabaseNextDay := myDatabaseDate + 1;

  SELECT something into some_var
  FROM MYDATABASE 
  WHERE inputDate < myDatabaseNextDay
  AND inputDate >= myDatabaseDate; 

  ...

Note 1: Because "inputDate" is a database column and could be indexed, we don't want to do TRUNC(inputDate) because then the index won't be used.

Note 2: Doing the CAST before the SQL statement prevents this PL/SQL compilation warning: PLW-07204: conversion away from column type may result in sub-optimal query plan ... Edit: After testing this on 10.2 XE, even the "myDatabaseDate + 1" causes the warning so, although it seems like doing too much to please the compiler, I added "myDatabaseNextDay := myDatabaseDate + 1;"

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How to make stored procedure with outputs OUT sys_refcursor, OUT varchar2, and OUT number, then use in c#.net app

Your procedure is missing two OUT parameters:

PROCEDURE myprocedure (myinput      IN Varchar2, 
                       myretcursor  OUT sys_refcursor,
                       p_count      OUT NUMBER,
                       p_message    OUT VARCHAR2) IS
BEGIN
   OPEN myretcursor FOR
      SELECT * FROM MYTABLE;
   p_count := 123;
   p_message := 'message';
END myprocedure

You would also need to modify your C# code to register the new OUT parameters accordingly.

Oracle extract slow function call from a WHERE clause

The second form of your query will work if you make your mark your function as deterministic, meaning that for a given set of input values, it will always return the same result.
With that set, Oracle will only run the conversion once for each parameters in the where clause rather than for every row.

With this:

CREATE OR REPLACE FUNCTION TO_MINUTE_D (DATE_IN IN DATE)
RETURN NUMBER DETERMINISTIC AS
BEGIN
  /* Minute 0 = 12/30/1899 12:00am */
  RETURN
    (TRUNC(DATE_IN, 'DD') - TO_DATE('12/30/1899', 'MM/DD/YYYY')) * 1440 +
    TO_NUMBER(TO_CHAR(DATE_IN, 'HH24'))  * 60 +
    TO_NUMBER(TO_CHAR(DATE_IN, 'MI'));
END TO_MINUTE_D;
/

On a table filled with a large bunch of dummy rows (increasing ints), I get the following timings consistently:

SQL> SELECT * FROM MY_TABLE
WHERE START_MINUTE < TO_MINUTE(TO_DATE('2013-01-31', 'YYYY-MM-DD'))
AND STOP_MINUTE > TO_MINUTE(TO_DATE('2013-01-01', 'YYYY-MM-DD'));

no rows selected

Elapsed: 00:00:12.69

versus deterministic-annotated function:

SQL> SELECT * FROM MY_TABLE
     WHERE START_MINUTE < TO_MINUTE_D(TO_DATE('2013-01-31', 'YYYY-MM-DD'))
     AND STOP_MINUTE > TO_MINUTE_D(TO_DATE('2013-01-01', 'YYYY-MM-DD')); 

no rows selected

Elapsed: 00:00:00.07

You should get very close to what you have with the values plugged in directly, and indexes on those columns can be used as if you'd plugged in literals.

(Putting the conversion function on the start|stop_minute columns isn't a good idea in general as you've discovered, unless you have a function-based index on those that matches exactly.)

Best Answer

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Oracle extract slow function call from a WHERE clause

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