2 step in a sql

Question

is there any way to do two passes?
The first sql will retrieve the date value from the some xyz function and store it in a variable.
The second sql is the 'select statement' sql with reference to the value derived from the previous step.
thanks.

Answer 1

Hi,
If you declare your function to be DETERMINISTIC, the optimizer won't need to call it every time it is referenced.
Just add the keyword DETERMINISTIC after the return type abd before AS or IS:
CREATE OR REPLACE FUNCTION instancesysdate
RETURN DATE
DETERMINISTIC
AS
    ...Other, less desireable alternatives include:
You can call the function once in a sub-query, and then join to the sub-query in your main query, which would probably be much faster than calling a user-defined function on every row. Depeneding on your verswion, you might need some trick, like adding "WHERE ROWNUM = 1" in the siub-query, to make sure it is only executed once.
You can also store the DATE variable in a regular table, or a Global Temporary Table, and join to that.
As someone already mentioned, there are no DATE bind variables, but storing a string representation of the DATE in a VARCHAR2 variable (or a substitution variable) would probably be faster than what you have now.