130823創建函數

SQL> create or replace function circle_area (
  2  p_radius in number
  3  ) return number as
  4  v_pi number := 3.1415926;
  5  v_area number;
  6  
  7  begin
  8    v_area := v_pi * power(p_radius, 2);
  9    return v_area;
 10  
 11  end circle_area;
 12  /
 
Function created
 
SQL> select circle_area(2) from dual;
 
CIRCLE_AREA(2)
--------------
    12.5663704

SQL> create or replace function average_product_price(
  2  p_product_type_id in integer
  3  ) return number as
  4  v_average_product_price number;
  5  
  6  begin
  7    select avg(price)
  8    into v_average_product_price
  9    from products
 10    where product_type_id = p_product_type_id;
 11    return v_average_product_price;
 12  end average_product_price;
 13  /
 
Warning: Function created with compilation errors
 
SQL> show error;
Errors for FUNCTION CALVIN.AVERAGE_PRODUCT_PRICE:
 
LINE/COL ERROR
-------- -----------------------------------------------
9/8      PL/SQL: ORA-00942: table or view does not exist
7/3      PL/SQL: SQL Statement ignored
 
SQL> 
SQL> create or replace function average_product_price(
  2  p_product_type_id in integer
  3  ) return number as
  4  v_average_product_price number;
  5  
  6  begin
  7    select avg(price)
  8    into v_average_product_price
  9    from store.products
 10    where product_type_id = p_product_type_id;
 11    return v_average_product_price;
 12  end average_product_price;
 13  /
 
Function created
 
SQL> select calvin.average_product_price(1) from dual;
 
CALVIN.AVERAGE_PRODUCT_PRICE(1
------------------------------
                       22.4825
 

這裏需要注意，查詢函數使用user_procedures視圖，系統中不存在users_functions視圖；

SQL> select * from user_procedures;
 
OBJECT_NAME                                                                      PROCEDURE_NAME                  OBJECT_ID SUBPROGRAM_ID OVERLOAD                                 OBJECT_TYPE         AGGREGATE PIPELINED IMPLTYPEOWNER                  IMPLTYPENAME                   PARALLEL INTERFACE DETERMINISTIC AUTHID
-------------------------------------------------------------------------------- ------------------------------ ---------- ------------- ---------------------------------------- ------------------- --------- --------- ------------------------------ ------------------------------ -------- --------- ------------- ------------
AVERAGE_PRODUCT_PRICE                                                                                                75103             1                                          FUNCTION            NO        NO                                                                      NO       NO        NO            DEFINER
UPDATE_PRODUCT_PRICE                                                                                                 75101             1                                          PROCEDURE           NO        NO                                                                      NO       NO        NO            DEFINER
CIRCLE_AREA                                                                                                          75102             1                                          FUNCTION            NO        NO                                                                      NO       NO        NO            DEFINER
 

SQL> drop function circle_area;
 
Function dropped