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This article mainly explains "how to use the DETERMINISTIC function", the content of the article is simple and clear, easy to learn and understand, the following please follow the editor's ideas slowly in depth, together to study and learn "how to use the DETERMINISTIC function" bar!

I defined the following functions:

FUNCTION plch_getdata (n NUMBER) RETURN NUMBERISBEGIN RETURN nterend

Which options include code that will improve performance if I add the above function to the DETERMINISTIC keyword?

Two points should be noted:

1. In one of the options, this function is "redefined" as an embedded subroutine.

two。 Two of these options contain queries executed in ALL_SOURCE, and you can assume that there are more than 1000000 lines of code in this view.

(A)

DECLARE n NUMBER;BEGIN FOR rec IN (SELECT plch_getdata (1) n FROM all_source WHERE ROWNUM < 1000000) LOOP n: = rec.n; END LOOP;END;/

(B)

DECLARE n NUMBER;BEGIN FOR indx IN 1.. 10000000 LOOP n: = plch_getdata (1); END LOOP;END;/

(C)

DECLARE n NUMBER; FUNCTION plch_getdata (n NUMBER) RETURN NUMBER DETERMINISTIC IS BEGIN RETURN n; END;BEGIN FOR indx IN 1.. 10000000 LOOP n: = plch_getdata (1); END LOOP;END;/

(D)

DECLARE n NUMBER;BEGIN FOR rec IN (SELECT plch_getdata (ROWNUM) n FROM all_source WHERE ROWNUM < 1000000) LOOP n: = rec.n; END LOOP;END;/

Answer AB.

Both An and B repeatedly call the same function and use the same parameters. With the addition of deterministic, the result of the function is cached and only called once.

C: syntax error, deterministic cannot be used in nested subroutines.

D: the parameters change each time and cannot be cached.

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