Nested Tables

[表中有表]

关联数组，是用在PL/SQL中的一种普通数据类型，无法存储在数据库中；嵌套表既可以在PL/SQL中使用，也可以存储在数据库中.

VARRAY

可变数组，既可以在PL/SQL中使用，也可以存储在数据库中.

Summary of Collection Types

Quiz

Identify situations in which you can use the %ROWTYPE attribute.

1. When you are not sure about the structure of the underlying database table.
2. When you want to retrieve an entire row from a table.
3. When you want to declare a variable according to another previously declared bariable or database column.

锚锁定技术有两类，一类是Scalar变量的锁定，一类是Record的锁定；Scalar的锁定使用%TYPE,Record的锁定使用%ROWTYPE;

Summary

In this lesson,you should have learned to:

• Define and reference PL/SQL variables of composite data types
  • -PL/SQL record
  • -Associative array
    • -INDEX BY table
    • -INDEX BY table of records
• Define a PL/SQL record by using the %ROWTYPE attribute
• Compare and contrast the three PL/SQL collection types:
  • -Associative array
  • -Nested table
  • -VARRAY