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采用bulk collect可以將查詢(xún)結(jié)果一次性地加載到collections中。

而不是通過(guò)cursor一條一條地處理。

可以在select into,fetch into,returning into語(yǔ)句使用bulk collect。

注意在使用bulk collect時(shí)，所有的into變量都必須是collections.

 

舉幾個(gè)簡(jiǎn)單的例子：

--在select into語(yǔ)句中使用bulk collect

DECLARE
TYPE SalList IS TABLE OF emp.sal%TYPE;
sals SalList;
BEGIN
-- Limit the number of rows to 100.
SELECT sal BULK COLLECT INTO sals FROM emp
WHERE ROWNUM <= 100;
-- Retrieve 10% (approximately) of the rows in the table.
SELECT sal BULK COLLECT INTO sals FROM emp SAMPLE 10;

END;
/

--在fetch into中使用bulk collect

DECLARE
TYPE DeptRecTab IS TABLE OF dept%ROWTYPE;
dept_recs DeptRecTab;
CURSOR c1 IS
SELECT deptno, dname, loc FROM dept WHERE deptno > 10;
BEGIN
OPEN c1;
FETCH c1 BULK COLLECT INTO dept_recs;
END;
/

--在returning into中使用bulk collect

CREATE TABLE emp2 AS SELECT * FROM employees;
DECLARE
TYPE NumList IS TABLE OF employees.employee_id%TYPE;
enums NumList;
TYPE NameList IS TABLE OF employees.last_name%TYPE;
names NameList;
BEGIN
DELETE FROM emp2 WHERE department_id = 30
RETURNING employee_id, last_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('Employee #' || enums(i) || ': ' || names(i));
END LOOP;
END;
/
DROP TABLE emp2;