ORACLE批量绑定FORALL与BULK COLLECT

FORALL与BULK COLLECT的使用方法:

1．使用FORALL比FOR效率高，因为前者只切换一次上下文，而后者将是在循环次数一样多个上下文间切换。

2．使用BLUK COLLECT一次取出一个数据集合，比用游标条取数据效率高，尤其是在网络不大好的情况下。但BLUK COLLECT需要大量内存。

例子:

Sql代码



create table test_forall ( user_id number(10), user_name varchar2(20));

select into 中使用bulk collect

Sql代码



DECLARE

TYPE table_forall IS TABLE OF test_forall%ROWTYPE;

v_table table_forall;

BEGIN

SELECT mub.user_id,mub.user_name

BULK COLLECT INTO v_table

FROM mag_user_basic mub

WHERE mub.user_id BETWEEN 10000 AND 10100;

FORALL idx IN 1..v_table.COUNT

INSERT INTO test_forall VALUES v_table(idx);

--VALUES(v_table(idx).user_id,v_table(idx).user_name);Error

--在PL/SQL中，BULK In-BIND与RECORD，%ROWTYPE是不能在一块使用的，

--也就是说，BULK In-BIND只能与简单类型的数组一块使用

COMMIT;

EXCEPTION

WHEN OTHERS THEN

ROLLBACK;

END;

fetch into 中使用bulk collect

Sql代码



DECLARE

TYPE table_forall IS TABLE OF test_forall%ROWTYPE;

v_table table_forall;

CURSOR c1 IS

SELECT mub.user_id,mub.user_name

FROM mag_user_basic mub

WHERE mub.user_id BETWEEN 10000 AND 10100;

BEGIN

OPEN c1;

--在fetch into中使用bulk collect

FETCH c1 BULK COLLECT INTO v_table;

FORALL idx IN 1..v_table.COUNT

INSERT INTO test_forall VALUES v_table(idx);

COMMIT;

EXCEPTION

WHEN OTHERS THEN

ROLLBACK;

END;

在returning into中使用bulk collect

Sql代码



CREATE TABLE test_forall2 AS SELECT * FROM test_forall;

----在returning into中使用bulk collect

DECLARE

TYPE IdList IS TABLE OF test_forall.User_Id%TYPE;

enums IdList;

TYPE NameList IS TABLE OF test_forall.user_name%TYPE;

names NameList;

BEGIN

DELETE FROM test_forall2 WHERE user_id = 10100

RETURNING user_id, user_name BULK COLLECT INTO enums, names;

dbms_output.put_line('Deleted ' || SQL%ROWCOUNT || ' rows:');

FOR i IN enums.FIRST .. enums.LAST

LOOP

dbms_output.put_line('User #' || enums(i) || ': ' || names(i));

END LOOP;

COMMIT;

EXCEPTION

WHEN OTHERS THEN

ROLLBACK;

END;

批量更新中，将for改成forall

Sql代码



DECLARE

TYPE NumList IS VARRAY(20) OF NUMBER;

depts NumList := NumList(10, 30, 70, ...);

-- department numbers

BEGIN

...

FOR i IN depts.FIRST..depts.LAST

LOOP

...

--UPDATE statement is sent to the SQL engine

-- with each iteration of the FOR loop!

UPDATE emp SET sal = sal * 1.10 WHERE deptno = depts(i);

END LOOP:

END;

Sql代码



--UPDATE statement is sent to the SQL engine just once, with the entire nested table

FORALL i IN depts.FIRST..depts.LAST

UPDATE emp SET sal = sal * 1.10 WHERE deptno = depts(i);

To maximize performance, rewrite your programs as follows:

a. If an INSERT, UPDATE, or DELETE statement executes inside a loop and References collection elements, move it into a FORALL statement.

b. If a SELECT INTO, FETCH INTO, or RETURNING INTO clause references a

Collection, incorporate the BULK COLLECT clause.

c. If possible, use host arrays to pass collections back and forth between your Programs and the database server.

d. If the failure of a DML operation on a particular row is not a serious problem,Include the keywords SAVE EXCEPTIONS in the FORALL statement and report Or clean up the errors in a subsequent loop using the %BULK_EXCEPTIONS Attribute.