📅 最后修改于: 2020-11-26 05:58:00 🧑 作者: Mango
在本章中，我们将讨论PL / SQL中的Records。记录是可以容纳不同种类数据项的数据结构。记录由不同的字段组成，类似于数据库表的一行。
例如，您想跟踪图书馆中的书籍。您可能需要跟踪有关每本书的以下属性，例如标题，作者，主题，书ID。包含每个项目的字段的记录允许将BOOK视为逻辑单元，并允许您以更好的方式组织和表示其信息。
PL / SQL可以处理以下类型的记录-
％ROWTYPE属性使程序员可以创建基于表和基于游标的记录。
以下示例说明了基于表的记录的概念。我们将使用在先前各章中创建并使用的CUSTOMERS表-
DECLARE
customer_rec customers%rowtype;
BEGIN
SELECT * into customer_rec
FROM customers
WHERE id = 5;
dbms_output.put_line('Customer ID: ' || customer_rec.id);
dbms_output.put_line('Customer Name: ' || customer_rec.name);
dbms_output.put_line('Customer Address: ' || customer_rec.address);
dbms_output.put_line('Customer Salary: ' || customer_rec.salary);
END;
/
当以上代码在SQL提示符下执行时，将产生以下结果-
Customer ID: 5
Customer Name: Hardik
Customer Address: Bhopal
Customer Salary: 9000
PL/SQL procedure successfully completed.
下面的示例说明了基于游标的记录的概念。我们将使用在先前各章中创建并使用的CUSTOMERS表-
DECLARE
CURSOR customer_cur is
SELECT id, name, address
FROM customers;
customer_rec customer_cur%rowtype;
BEGIN
OPEN customer_cur;
LOOP
FETCH customer_cur into customer_rec;
EXIT WHEN customer_cur%notfound;
DBMS_OUTPUT.put_line(customer_rec.id || ' ' || customer_rec.name);
END LOOP;
END;
/
当以上代码在SQL提示符下执行时，将产生以下结果-
1 Ramesh
2 Khilan
3 kaushik
4 Chaitali
5 Hardik
6 Komal
PL/SQL procedure successfully completed.
PL / SQL提供了用户定义的记录类型，使您可以定义不同的记录结构。这些记录包含不同的字段。假设您想跟踪图书馆中的书籍。您可能需要跟踪每本书的以下属性-
记录类型定义为-
TYPE
type_name IS RECORD
( field_name1 datatype1 [NOT NULL] [:= DEFAULT EXPRESSION],
field_name2 datatype2 [NOT NULL] [:= DEFAULT EXPRESSION],
...
field_nameN datatypeN [NOT NULL] [:= DEFAULT EXPRESSION);
record-name type_name;
Book记录通过以下方式声明-
DECLARE
TYPE books IS RECORD
(title varchar(50),
author varchar(50),
subject varchar(100),
book_id number);
book1 books;
book2 books;
要访问记录的任何字段，我们使用点(。)运算符。成员访问运算符被编码为记录变量名称和我们希望访问的字段之间的句点。以下是解释记录用法的示例-
DECLARE
type books is record
(title varchar(50),
author varchar(50),
subject varchar(100),
book_id number);
book1 books;
book2 books;
BEGIN
-- Book 1 specification
book1.title := 'C Programming';
book1.author := 'Nuha Ali ';
book1.subject := 'C Programming Tutorial';
book1.book_id := 6495407;
-- Book 2 specification
book2.title := 'Telecom Billing';
book2.author := 'Zara Ali';
book2.subject := 'Telecom Billing Tutorial';
book2.book_id := 6495700;
-- Print book 1 record
dbms_output.put_line('Book 1 title : '|| book1.title);
dbms_output.put_line('Book 1 author : '|| book1.author);
dbms_output.put_line('Book 1 subject : '|| book1.subject);
dbms_output.put_line('Book 1 book_id : ' || book1.book_id);
-- Print book 2 record
dbms_output.put_line('Book 2 title : '|| book2.title);
dbms_output.put_line('Book 2 author : '|| book2.author);
dbms_output.put_line('Book 2 subject : '|| book2.subject);
dbms_output.put_line('Book 2 book_id : '|| book2.book_id);
END;
/
当以上代码在SQL提示符下执行时，将产生以下结果-
Book 1 title : C Programming
Book 1 author : Nuha Ali
Book 1 subject : C Programming Tutorial
Book 1 book_id : 6495407
Book 2 title : Telecom Billing
Book 2 author : Zara Ali
Book 2 subject : Telecom Billing Tutorial
Book 2 book_id : 6495700
PL/SQL procedure successfully completed.
您可以像传递任何其他变量一样，将记录作为子程序参数传递。您还可以按照与上述示例相同的方式访问记录字段-
DECLARE
type books is record
(title varchar(50),
author varchar(50),
subject varchar(100),
book_id number);
book1 books;
book2 books;
PROCEDURE printbook (book books) IS
BEGIN
dbms_output.put_line ('Book title : ' || book.title);
dbms_output.put_line('Book author : ' || book.author);
dbms_output.put_line( 'Book subject : ' || book.subject);
dbms_output.put_line( 'Book book_id : ' || book.book_id);
END;
BEGIN
-- Book 1 specification
book1.title := 'C Programming';
book1.author := 'Nuha Ali ';
book1.subject := 'C Programming Tutorial';
book1.book_id := 6495407;
-- Book 2 specification
book2.title := 'Telecom Billing';
book2.author := 'Zara Ali';
book2.subject := 'Telecom Billing Tutorial';
book2.book_id := 6495700;
-- Use procedure to print book info
printbook(book1);
printbook(book2);
END;
/
当以上代码在SQL提示符下执行时，将产生以下结果-
Book title : C Programming
Book author : Nuha Ali
Book subject : C Programming Tutorial
Book book_id : 6495407
Book title : Telecom Billing
Book author : Zara Ali
Book subject : Telecom Billing Tutorial
Book book_id : 6495700
PL/SQL procedure successfully completed.