ORA-06531: Reference to uninitialized collection
Cause: An element or member function of a nested table or varray was referenced (where an initialized collection is needed) without the collection having been initialized.
Action: Initialize the collection with an appropriate constructor or whole-object assignment.
ORA-06531 错误是一种基于无法访问未初始化集合的异常。它允许系统将未初始化集合的权限分配给未定义的变量，该变量可能已经定义为其他类型。