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Oracle 11g Release 1 (11.1) PL/SQL_理解 Collection 类型

2012-05-13 18:44 495 查看

http://docs.oracle.com/cd/B28359_01/appdev.111/b28370/collections.htm#CIHIEBJC

本文内容

定义 Collection 类型
声明 Collection 变量
初始化和引用 Collection
引用 Collection 元素
给 Collection 赋值
多维 Collection
比较 Collection
Collection 方法
Collection 异常

了解 Oracle 集合意义在于：当我们采用编程语言开发应用程序时，对其内置的集合类型，如数组、链表等，使用得很多，也很方便，但是当业务逻辑变得复杂时，如需要同时向多个表插入数据，和一个表插入多条数据，也许还需要事物控制，此时使用匿名子程序似乎很合适。那么，在匿名子程序中使用集合类型就不可避免。

另外，若有一个用编程语言写的函数，其涉及集合操作，出于某种必要的原因，想改写成 Oracle 函数，那么，对了解 Oracle 集合操作很有必要。

定义 Collection 类型

先定义 collection 类型，之后再声明该类型的变量。

你可以在模式级别、包或 PL/SQL 块内定义一个 collection 类型。

在模式级别创建的 collection 类型是 standalone stored type。用 CREATE TYPE 语句创建。它存储在数据库，直到用 DROP TYPE 语句删除该类型。

在包内创建的 collection 类型是 packaged type。它存储在数据库，直到用 DROP PACKAGE 语句删除包。

在 PL/SQL 块创建的 collection 类型只在块内可用，只有块嵌入在 standalone 或 packaged subprogram 中它才存储在数据库。

collection 类型遵循与其他类型、变量一样的作用域和实例化规则。当你输入一个块或子程序时，collection 被实例化，当退出时，销毁。在一个包中，当初从引用包时，collection 被实例化，并在结束数据库会话时，销毁。

你可以在任何 PL/SQL 块、子程序，或包的声明部分，使用 TYPE 来定义 TABLE 和 VARRAY 类型。

对于在 PL/SQL 内声明的 nested table 和 varray，table 或 varray 的元素类型可以是，除了 REF CURSOR 以外的任意 PL/SQL 数据类型。

当定义一个 VARRAY 类型时，必须用一个正整数指定最大大小。如下所示，定义一个能最多存储 366 个日期的 VARRAY：

[code]DECLARE
TYPE Calendar IS VARRAY(366) OF DATE;

[/code]

associative arrays 可以用任意键值插入元素。键不需要是连续的。键的数据类型可以是 PLS_INTEGER、VARCHAR2，或 VARCHAR2 子类型的一个：VARCHAR、STRING、或 LONG.

必须指定基于 VARCHAR2 键的长度，除了 LONG，因为，它等价于声明一个 VARCHAR2(32760) 类型的键。类型 RAW、LONG RAW、ROWID、CHAR 和 CHARACTER 不允许做为一个 associative array 的键。LONG 和 LONG RAW 仅仅是为了向后兼容。

不允许初始化子句。associative arrays 没有构造标记。当使用基于 VARCHAR2 键来引用 associative arrays 中的一个元素时，你可以使用如 DATE 或 TIMESTAMP 等类型，只要该类型可以用 TO_CHAR 函数转换成 VARCHAR2。

声明 Collection 变量

定义一个 collection 类型后，用该类型声明变量。在声明中使用新类型名，同预定义类型一样，如 NUMBER。

示例 1：演示声明 nested table、varray 和 associative array

DECLARE


[code]  TYPE nested_type IS TABLE OF VARCHAR2(30);

TYPE varray_type IS VARRAY(5) OF INTEGER;

TYPE assoc_array_num_type IS TABLE OF NUMBER INDEX BY PLS_INTEGER;

TYPE assoc_array_str_type IS TABLE OF VARCHAR2(32) INDEX BY PLS_INTEGER;

TYPE assoc_array_str_type2 IS TABLE OF VARCHAR2(32) INDEX BY VARCHAR2(64);

v1 nested_type;

v2 varray_type;

v3 assoc_array_num_type;

v4 assoc_array_str_type;

v5 assoc_array_str_type2;

BEGIN

-- an arbitrary number of strings can be inserted v1

v1 := nested_type('Shipping', 'Sales', 'Finance', 'Payroll');

v2 := varray_type(1, 2, 3, 4, 5); -- Up to 5 integers

v3(99) := 10; -- Just start assigning to elements

v3(7) := 100; -- Subscripts can be any integer values

v4(42) := 'Smith'; -- Just start assigning to elements

v4(54) := 'Jones'; -- Subscripts can be any integer values

v5('Canada') := 'North America';

-- Just start assigning to elements

v5('Greece') := 'Europe';

-- Subscripts can be string values

END;

[/code]

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示例 2：演示用 %TYPE 声明 Collection

使用 %TYPE 指定之前已声明的 collection 类型，改变 collection 定义，会根据元素数量和类型自动更新其他变量。

DECLARE


[code]  TYPE few_depts  IS VARRAY(10)  OF VARCHAR2(30);

TYPE many_depts IS VARRAY(100) OF VARCHAR2(64);

some_depts few_depts;

/* If the type of some_depts changes from few_depts to many_depts,

local_depts and global_depts will use the same type

when this block is recompiled */

local_depts  some_depts%TYPE;

global_depts some_depts%TYPE;

BEGIN

NULL;

END;

[/code]

示例 3：演示声明一个 nested Table 作为存储过程的参数

声明 collection 为子程序的形参，把 collection 从一个子程序传递给另一个子程序。

CREATE PACKAGE personnel AS


[code]TYPE staff_list IS TABLE OF employees.employee_id%TYPE;

PROCEDURE award_bonuses (empleos_buenos IN staff_list);

END personnel;

CREATE PACKAGE BODY personnel AS

PROCEDURE award_bonuses (empleos_buenos staff_list) IS

BEGIN

FOR i IN empleos_buenos.FIRST..empleos_buenos.LAST

LOOP

UPDATE employees SET salary = salary + 100

WHERE employees.employee_id = empleos_buenos(i);

END LOOP;

END;

END;

DECLARE


[code]  good_employees personnel.staff_list;

BEGIN

good_employees :=  personnel.staff_list(100, 103, 107);

personnel.award_bonuses (good_employees);

END;

DECLARE


[code]-- Nested table type that can hold an arbitrary number

--of employee IDs.

-- The element type is based on a column from the EMPLOYEES table.

-- You need not know whether the ID is a number or a string.

TYPE EmpList IS TABLE OF employees.employee_id%TYPE;

-- Declare a cursor to select a subset of columns.

CURSOR c1 IS SELECT employee_id FROM employees;

-- Declare an Array type that can hold information

--about 10 employees.

-- The element type is a record that contains all the same

-- fields as the EMPLOYEES table.

TYPE Senior_Salespeople IS VARRAY(10) OF employees%ROWTYPE;

-- Declare a cursor to select a subset of columns.

CURSOR c2 IS SELECT first_name, last_name FROM employees;

-- Array type that can hold a list of names. The element type

-- is a record that contains the same fields as the cursor

-- (that is, first_name and last_name).

TYPE NameList IS VARRAY(20) OF c2%ROWTYPE;

BEGIN

 NULL;

END;

DECLARE


[code]  TYPE name_rec IS RECORD(

first_name VARCHAR2(20),

last_name  VARCHAR2(25));

TYPE names IS VARRAY(250) OF name_rec;

BEGIN

NULL;

END;

DECLARE


[code]  TYPE EmpList IS TABLE OF employees.employee_id%TYPE NOT NULL;

v_employees EmpList := EmpList(100, 150, 160, 200);

BEGIN

v_employees(3) := NULL; -- assigning NULL raises an exception

END;

初始化和引用 Collection

初始化时，一个 nested table 或 varray 会自动为 null。collection 本身为 null，它没有元素。若初始化一个 nested table 或 varray，可以使用系统预定义的构造函数，该构造函数与 collection 类型名同名，通过传递给它的元素构造 collection。

必须显示为 nested table 和 varray 变量调用构造函数。而 associative array 则不需要这样。

示例 7：演示构造 nested table

DECLARE


[code]TYPE dnames_tab IS TABLE OF VARCHAR2(30);

dept_names dnames_tab;

BEGIN

dept_names := dnames_tab('Shipping','Sales','Finance','Payroll');

END;

DECLARE


[code]-- In the varray, put an upper limit on the number of elements

TYPE dnames_var IS VARRAY(20) OF VARCHAR2(30);

dept_names dnames_var;

BEGIN

-- Because dnames is declared as VARRAY(20),

-- you can put up to 10 elements in the constructor

dept_names := dnames_var('Shipping','Sales','Finance','Payroll');

END;

[/code]

示例 9：演示 [b]Collection 构造函数包含 Null 元素 [/b]

DECLARE


[code]TYPE dnames_tab IS TABLE OF VARCHAR2(30);

dept_names dnames_tab;

TYPE dnamesNoNulls_type IS TABLE OF VARCHAR2(30) NOT NULL;

BEGIN

dept_names := dnames_tab('Shipping', NULL,'Finance', NULL);

-- If dept_names were of type dnamesNoNulls_type,

--  you could not include null values in the constructor

END;

DECLARE


[code]TYPE dnames_tab IS TABLE OF VARCHAR2(30);

dept_names dnames_tab :=

dnames_tab('Shipping','Sales','Finance','Payroll');

BEGIN

 NULL;

END;

[/code]

示例 11：演示无参数的 varray 构造函数，会得到一个空的，而不是 null 的 collection

DECLARE


[code]TYPE dnames_var IS VARRAY(20) OF VARCHAR2(30);

dept_names dnames_var;

BEGIN

IF dept_names IS NULL THEN

DBMS_OUTPUT.PUT_LINE

('Before initialization, the varray is null.');

-- While the varray is null, you cannot check its COUNT attribute.

-- DBMS_OUTPUT.PUT_LINE

-- ('It has ' || dept_names.COUNT || ' elements.');

ELSE

DBMS_OUTPUT.PUT_LINE

('Before initialization, the varray is not null.');

END IF;

dept_names := dnames_var(); -- initialize empty varray

IF dept_names IS NULL THEN

DBMS_OUTPUT.PUT_LINE

('After initialization, the varray is null.');

ELSE

DBMS_OUTPUT.PUT_LINE

('After initialization, the varray is not null.');

DBMS_OUTPUT.PUT_LINE

('It has ' || dept_names.COUNT || ' elements.');

END IF;

END;

引用 Collection 元素

引用元素包括一个 collection 名字和用大括号括起来的标值（subscript）。通过下面语法：

collection_name (subscript)

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这里的“标值”，通常，是一个返回整数值的表达式，或用字符串声明的 associative arrays 键，它是一个 VARCHAR2。

标值的范围如下：

对于 nested tables，1..2147483647 （上限是 PLS_INTEGER）。

对于 varrays，1.. size_limit，你在声明中指定的大小，size_limit 不能超过 2147483647。

对于带数字型键的 associative arrays，-2147483648..2147483647。

对于带字符串键的 associative arrays，键的长度和可能值的数量依赖于类型声明中 VARCHAR2 的限制，和数据库字符集。

示例 12：演示引用 nested table 元素

DECLARE


[code]  TYPE Roster IS TABLE OF VARCHAR2(15);

names Roster :=

Roster('D Caruso', 'J Hamil', 'D Piro', 'R Singh');

PROCEDURE verify_name(the_name VARCHAR2) IS

BEGIN

DBMS_OUTPUT.PUT_LINE(the_name);

END;

BEGIN

FOR i IN names.FIRST .. names.LAST

LOOP

IF names(i) = 'J Hamil' THEN

DBMS_OUTPUT.PUT_LINE(names(i));

-- reference to nested table element

END IF;

END LOOP;

verify_name(names(3));

-- procedure call with reference to element

END;

[/code]

示例 13：演示引用 associative array 元素

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DECLARE


[code]  TYPE sum_multiples IS TABLE OF PLS_INTEGER INDEX BY PLS_INTEGER;

n  PLS_INTEGER := 5;-- number of multiples to sum for display

sn PLS_INTEGER := 10;  -- number of multiples to sum

m  PLS_INTEGER := 3;-- multiple

FUNCTION get_sum_multiples

(multiple IN PLS_INTEGER, num IN PLS_INTEGER)

RETURN sum_multiples IS

s sum_multiples;

BEGIN

FOR i IN 1..num LOOP

s(i) := multiple * ((i * (i + 1)) / 2);

-- sum of multiples

 END LOOP;

RETURN s;

END get_sum_multiples;

BEGIN

-- invoke function to retrieve

-- element identified by subscript (key)

DBMS_OUTPUT.PUT_LINE

('Sum of the first ' || TO_CHAR(n) || ' multiples of ' ||

TO_CHAR(m) || ' is ' || TO_CHAR(get_sum_multiples (m, sn)(n)));

END;

[/code]

给 Collection 赋值

一个 collection 可以通过 INSERT、UPDATE、FETCH 或 SELECT 语句赋值。通过下面语法，把表达式值赋给 collection 中的一个指定元素：

collection_name (subscript) := expression;

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其中，表达式值与类型兼容。

可以使用 SET、MULTISET UNION、MULTISET INTERSECT 和 MULTISET EXCEPT 操作符把 nested tables 转换成赋值语句的一部分。

下面情况，赋一个值给 collection 元素会产生异常：

若标值为 NULL 或不能转换成正确的数据类型，PL/SQL 会产生异常 VALUE_ERROR。通常，标值必须是整数。associative arrays 也可以有 VARCHAR2 标值。

若标值引用一个为初始化的元素，则 PL/SQL 会产生异常 SUBSCRIPT_BEYOND_COUNT。

若 collection （自动）为 null，则 PL/SQL 会产生异常 COLLECTION_IS_NULL。

示例 14：演示 Collection 类型兼容赋值

DECLARE


[code]TYPE last_name_typ IS VARRAY(3) OF VARCHAR2(64);

TYPE surname_typ IS VARRAY(3) OF VARCHAR2(64);

-- These first two variables have the same data type.

group1 last_name_typ := last_name_typ('Jones','Wong','Marceau');

group2 last_name_typ := last_name_typ('Klein','Patsos','Singh');

-- This third variable has a similar declaration,

-- but is not the same type.

group3 surname_typ := surname_typ('Trevisi','Macleod','Marquez');

BEGIN

-- Allowed because they have the same data type

group1 := group2;

-- Not allowed because they have different data types

--group3 := group2; -- raises an exception

END;

[/code]

示例 15：演示 nested table 赋值为 Null。

若把一个自动为 null 的 nested table 或 varray 赋值给另一个 nested table 或 varray，则另一个 collection 必须重新初始化。同样，把一个 collection 赋值为 NULL，它自动为 null。

DECLARE


[code]TYPE dnames_tab IS TABLE OF VARCHAR2(30);

-- This nested table has some values

dept_names dnames_tab :=

dnames_tab('Shipping','Sales','Finance','Payroll');

-- This nested table is not initialized ("atomically null").

empty_set dnames_tab;

BEGIN

-- At first, the initialized variable is not null.

if dept_names IS NOT NULL THEN

DBMS_OUTPUT.PUT_LINE('OK, at first dept_names is not null.');

END IF;

-- Then assign a null nested table to it.

dept_names := empty_set;

-- Now it is null.

if dept_names IS NULL THEN

DBMS_OUTPUT.PUT_LINE('OK, now dept_names has become null.');

END IF;

-- Use another constructor to give it some values.

dept_names := dnames_tab('Shipping','Sales','Finance','Payroll');

END;

DECLARE


[code]  TYPE nested_typ IS TABLE OF NUMBER;

nt1 nested_typ := nested_typ(1,2,3);

nt2 nested_typ := nested_typ(3,2,1);

nt3 nested_typ := nested_typ(2,3,1,3);

nt4 nested_typ := nested_typ(1,2,4);

answer nested_typ;

-- The results might be in a different order than you expect.

-- Do not rely on the order of elements in nested tables.

PROCEDURE print_nested_table(the_nt nested_typ) IS

output VARCHAR2(128);

BEGIN

IF the_nt IS NULL THEN

DBMS_OUTPUT.PUT_LINE('Results: <NULL>');

RETURN;

END IF;

IF the_nt.COUNT = 0 THEN

DBMS_OUTPUT.PUT_LINE('Results: empty set');

RETURN;

END IF;

FOR i IN the_nt.FIRST .. the_nt.LAST

 LOOP

output := output || the_nt(i) || ' ';

END LOOP;

DBMS_OUTPUT.PUT_LINE('Results: ' || output);

END;

BEGIN

answer := nt1 MULTISET UNION nt4; -- (1,2,3,1,2,4)

print_nested_table(answer);

answer := nt1 MULTISET UNION nt3; -- (1,2,3,2,3,1,3)

print_nested_table(answer);

answer := nt1 MULTISET UNION DISTINCT nt3; -- (1,2,3)

print_nested_table(answer);

answer := nt2 MULTISET INTERSECT nt3; -- (3,2,1)

print_nested_table(answer);

answer := nt2 MULTISET INTERSECT DISTINCT nt3; -- (3,2,1)

print_nested_table(answer);

answer := SET(nt3); -- (2,3,1)

print_nested_table(answer);

answer := nt3 MULTISET EXCEPT nt2; -- (3)

print_nested_table(answer);

answer := nt3 MULTISET EXCEPT DISTINCT nt2; -- ()

print_nested_table(answer);

END;

DECLARE


[code]  TYPE emp_name_rec is RECORD (

firstnameemployees.first_name%TYPE,

lastname employees.last_name%TYPE,

hiredate employees.hire_date%TYPE

);

-- Array type that can hold information 10 employees

TYPE EmpList_arr IS VARRAY(10) OF emp_name_rec;

SeniorSalespeople EmpList_arr;

-- Declare a cursor to select a subset of columns.

CURSOR c1 IS SELECT first_name, last_name, hire_date

 FROM employees;

Type NameSet IS TABLE OF c1%ROWTYPE;

SeniorTen NameSet;

EndCounter NUMBER := 10;

BEGIN

SeniorSalespeople := EmpList_arr();

SELECT first_name, last_name, hire_date

BULK COLLECT INTO SeniorTen

FROM employees

WHERE job_id = 'SA_REP'

ORDER BY hire_date;

IF SeniorTen.LAST > 0 THEN

IF SeniorTen.LAST < 10 THEN EndCounter := SeniorTen.LAST;

 END IF;

FOR i in 1..EndCounter LOOP

  SeniorSalespeople.EXTEND(1);

  SeniorSalespeople(i) := SeniorTen(i);

DBMS_OUTPUT.PUT_LINE(SeniorSalespeople(i).lastname || ', '

|| SeniorSalespeople(i).firstname || ', ' ||

SeniorSalespeople(i).hiredate);

 END LOOP;

END IF;

END;

DECLARE


[code]  TYPE emp_name_rec is RECORD (

firstnameemployees.first_name%TYPE,

lastname employees.last_name%TYPE,

hiredate employees.hire_date%TYPE

);

-- Table type that can hold information about employees

TYPE EmpList_tab IS TABLE OF emp_name_rec;

SeniorSalespeople EmpList_tab;

-- Declare a cursor to select a subset of columns.

CURSOR c1 IS SELECT first_name, last_name, hire_date

 FROM employees;

EndCounter NUMBER := 10;

TYPE EmpCurTyp IS REF CURSOR;

emp_cv EmpCurTyp;

BEGIN

OPEN emp_cv FOR SELECT first_name, last_name, hire_date

FROM employees

WHERE job_id = 'SA_REP' ORDER BY hire_date;

FETCH emp_cv BULK COLLECT INTO SeniorSalespeople;

CLOSE emp_cv;

-- for this example, display a maximum of ten employees

IF SeniorSalespeople.LAST > 0 THEN

IF SeniorSalespeople.LAST < 10 THEN

  EndCounter := SeniorSalespeople.LAST;

 END IF;

FOR i in 1..EndCounter LOOP

DBMS_OUTPUT.PUT_LINE

(SeniorSalespeople(i).lastname || ', '

 || SeniorSalespeople(i).firstname || ', ' || SeniorSalespeople(i).hiredate);

 END LOOP;

END IF;

END;

多维 Collection

/article/4963900.html

比较 Collections

可以检查一个 collection 是否为 null。不能进行大于、小于等比较。这个约束也适用于隐式比较。例如，collection 不能出现在 DISTINCT、GROUP BY 或 ORDER BY 里。

若想进行比较操作，必须自定义比较函数。

示例 19：演示检查一个 collection 是否为 NULL

nested table 和 varray 可以自动为 null，所以可以用 NULL 来测试。

DECLARE


[code]  TYPE emp_name_rec is RECORD (

firstnameemployees.first_name%TYPE,

lastname employees.last_name%TYPE,

hiredate employees.hire_date%TYPE

);

TYPE staff IS TABLE OF emp_name_rec;

members staff;

BEGIN

-- Condition yields TRUE because you have not used a constructor.

IF members IS NULL THEN

DBMS_OUTPUT.PUT_LINE('NULL');

ELSE

DBMS_OUTPUT.PUT_LINE('Not NULL');

END IF;

END;

[/code]

示例 20：演示比较两个 Nested Tables

nested tables 可以进行等于或不等于比较。但是它们不是按顺序的，不存在大于或小于比较。

DECLARE


[code]TYPE dnames_tab IS TABLE OF VARCHAR2(30);

dept_names1 dnames_tab :=

dnames_tab('Shipping','Sales','Finance','Payroll');

dept_names2 dnames_tab :=

 dnames_tab('Sales','Finance','Shipping','Payroll');

dept_names3 dnames_tab :=

 dnames_tab('Sales','Finance','Payroll');

BEGIN

-- You can use = or !=, but not < or >.

-- These 2 are equal even though members are in different order.

IF dept_names1 = dept_names2 THEN

DBMS_OUTPUT.PUT_LINE

  ('dept_names1 and dept_names2 have the same members.');

END IF;

IF dept_names2 != dept_names3 THEN

DBMS_OUTPUT.PUT_LINE

('dept_names2 and dept_names3 have different members.');

END IF;

END;

[/code]

示例 21：演示用 Set 操作符比较 nested tables

可以使用 ANSI-standard 的 Set 操作符，检查一个 nested table 的某个属性，或比较两个 nested table。

DECLARE


[code]  TYPE nested_typ IS TABLE OF NUMBER;

nt1 nested_typ := nested_typ(1,2,3);

nt2 nested_typ := nested_typ(3,2,1);

nt3 nested_typ := nested_typ(2,3,1,3);

nt4 nested_typ := nested_typ(1,2,4);

answer BOOLEAN;

howmany NUMBER;

PROCEDURE testify

(truth BOOLEAN DEFAULT NULL

 quantity NUMBER DEFAULT NULL) IS

BEGIN

IF truth IS NOT NULL THEN

DBMS_OUTPUT.PUT_LINE

(CASE truth WHEN TRUE THEN 'True' WHEN FALSE THEN 'False' END);

 END IF;

IF quantity IS NOT NULL THEN

DBMS_OUTPUT.PUT_LINE(quantity);

 END IF;

END;

BEGIN

answer := nt1 IN (nt2,nt3,nt4); -- true, nt1 matches nt2

testify(truth => answer);

answer := nt1 SUBMULTISET OF nt3; -- true, all elements match

testify(truth => answer);

answer := nt1 NOT SUBMULTISET OF nt4; -- also true

testify(truth => answer);

howmany := CARDINALITY(nt3); -- number of elements in nt3

testify(quantity => howmany);

howmany := CARDINALITY(SET(nt3)); -- number of distinct elements

testify(quantity => howmany);

answer := 4 MEMBER OF nt1; -- false, no element matches

testify(truth => answer);

answer := nt3 IS A SET; -- false, nt3 has duplicates

testify(truth => answer);

answer := nt3 IS NOT A SET; -- true, nt3 has duplicates

testify(truth => answer);

answer := nt1 IS EMPTY; -- false, nt1 has some members

testify(truth => answer);

END;

[/code]

Collection 方法

/article/4963897.html

Collection 异常

/article/4963900.html

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