User-Defined Aggregate Functions Interface（自定義聚合函式，也可作為分析函式）

ODCIAggregateInitialize()

Initializes the aggregation context and instance of the implementation object type, and returns it as an OUT parameter. F Implement this routine as a static method.

Syntax

STATIC FUNCTION ODCIAggregateInitialize(
   actx IN OUT ) 
RETURN NUMBER

actx

IN OUT

Returns

ODCIConst.Success on success, or ODCIConst.Error on error.

ODCIAggregateIterate()

Iterates through input rows by processesing the input values, updating and then returning the aggregation context. Invoked for each value, including NULLs. This is a mandatory routine and is implemented as a member method.

Syntax

MEMBER FUNCTION ODCIAggregateIterate(
   self IN OUT , 
   val ) RETURN NUMBER;

self

IN OUT

val

IN

Returns

ODCIConst.Success on success, or ODCIConst.Error on error.

ODCIAggregateMerge()

Merges two aggregation contexts into a single object instance during either serial or parallel evaluation of the user-defined aggregate. This is a mandatory routine and is implemented as a member method.

Syntax

MEMBER FUNCTION ODCIAggregateMerge(
   self IN OUT , 
   ctx2 IN ) RETURN NUMBER;

self

IN OUT

ctx2

IN

Returns

ODCIConst.Success on success, or ODCIConst.Error on error.

ODCIAggregateTerminate()

Calculates the result of the aggregate computation and performs all necessary cleanup, such as freeing memory. Invoked by Oracle as the last step of aggregate computation. This is a mandatory routine and is implemented as a member method.

Syntax

MEMBER FUNCTION ODCIAggregateTerminate(
   self IN , 
   ReturnValue OUT , 
   flags IN number) RETURN NUMBER;

self

IN

ctx2

OUT

flags

IN

Returns

ODCIConst.Success on success, or ODCIConst.Error on error.

ODCIAggregateDelete()

Removes an input value from the current group. The routine is invoked by Oracle by passing in the aggregation context and the value of the input to be removed during It processes the input value, updates the aggregation context, and returns the context. This is an optional routine and is implemented as a member method.

Syntax

MEMBER FUNCTION ODCIAggregateDelete(
   self IN OUT , 
   val ) RETURN NUMBER;

self

IN OUT

val

IN

Returns

ODCIConst.Success on success, or ODCIConst.Error on error.

ODCIAggregateWrapContext()

Integrates all external pieces of the current aggregation context to make the context self-contained. Invoked by Oracle if the user-defined aggregate has been declared to have external context and is transmitting partial aggregates from slave processes. This is an optional routine and is implemented as a member method.

Syntax

MEMBER FUNCTION ODCIAggregateWrapContext(
   self IN OUT ) RETURN NUMBER;

self

IN

Returns

ODCIConst.Success on success, or ODCIConst.Error on error.

e.g.

SQL> CREATE TABLE T AS SELECT ROWNUM ID, A.* FROM DBA_OBJECTS A;

表已建立。

SQL> CREATE OR REPLACE TYPE T_LINK AS OBJECT (
2 STR VARCHAR2(30000),
3 STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT T_LINK) RETURN NUMBER,
4 MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT T_LINK, VALUE IN VARCHAR2) RETURN NUMBER,
5 MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF IN T_LINK, RETURNVALUE OUT VARCHAR2, FLAGS IN NUMBE
R) RETURN NUMBER,
6 MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT T_LINK, CTX2 IN T_LINK) RETURN NUMBER
7 )
8 /

型別已建立。

SQL> CREATE OR REPLACE TYPE BODY T_LINK IS
2 STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT T_LINK) RETURN NUMBER IS
3 BEGIN
4 SCTX := T_LINK(NULL);
5 RETURN ODCICONST.SUCCESS;
6 END;
7
8 MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT T_LINK, VALUE IN VARCHAR2) RETURN NUMBER IS
9 BEGIN
10 SELF.STR := SELF.STR || VALUE || ',';
11 RETURN ODCICONST.SUCCESS;
12 END;
13
14 MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF IN T_LINK, RETURNVALUE OUT VARCHAR2, FLAGS IN NUMBE
R) RETURN NUMBER IS
15 BEGIN
16 RETURNVALUE := SUBSTR(SELF.STR, 1, LENGTH(SELF.STR) - 1);
17 RETURN ODCICONST.SUCCESS;
18 END;
19
20 MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT T_LINK, CTX2 IN T_LINK) RETURN NUMBER IS
21 BEGIN
22 NULL;
23 RETURN ODCICONST.SUCCESS;
24 END;
25 END;
26 /

型別主體已建立。

SQL> CREATE OR REPLACE FUNCTION F_LINK(P_STR VARCHAR2) RETURN VARCHAR2
2 AGGREGATE USING T_LINK;
3 /

函式已建立。

SQL> COL OWNER FORMAT A8
SQL> COL LINK_ID FORMAT A60
SQL> SELECT OWNER, F_LINK(ID) LINK_ID FROM T WHERE OWNER = 'SCOTT' GROUP BY OWNER;

OWNER LINK_ID
-------- -----------------------------------------------------------
SCOTT 32488,32489,32490,32492,32494,32501,32502,32495,32493,32491

目前聚集函式並沒有按照ID的順序排列。

SQL> SELECT OWNER, F_LINK(ID) OVER (ORDER BY ID) LINK_ID FROM T WHERE OWNER = 'SCOTT';

OWNER LINK_ID
-------- ------------------------------------------------------------
SCOTT 32488
SCOTT 32488,32489
SCOTT 32488,32489,32490
SCOTT 32488,32489,32490,32491
SCOTT 32488,32489,32490,32491,32492
SCOTT 32488,32489,32490,32491,32492,32493
SCOTT 32488,32489,32490,32491,32492,32493,32494
SCOTT 32488,32489,32490,32491,32492,32493,32494,32495
SCOTT 32488,32489,32490,32491,32492,32493,32494,32495,32501
SCOTT 32488,32489,32490,32491,32492,32493,32494,32495,32501,32502

已選擇10行。

可以看到，自定義的聚集函式也可以當作分析函式來使用。

下面簡單的取最大值就可以得到相應的結果。

SQL> SELECT OWNER, MAX(LINK_ID) LINK_ID FROM
2 (SELECT OWNER, F_LINK(ID) OVER (ORDER BY ID) LINK_ID
3 FROM T WHERE OWNER = 'SCOTT')
4 GROUP BY OWNER;

OWNER LINK_ID
-------- ------------------------------------------------------------
SCOTT 32488,32489,32490,32491,32492,32493,32494,32495,32501,32502

SQL> SELECT OWNER, MAX(LINK_ID) LINK_ID FROM
2 (SELECT OWNER, F_LINK(ID) OVER (ORDER BY ID DESC) LINK_ID
3 FROM T WHERE OWNER = 'SCOTT')
4 GROUP BY OWNER;