Oracle9i笔记1(6)

TIMESTAMP WITH TIME ZONE

TIMESTAMP WITH LOCAL TIME ZONE : This data type differs from TIMESTAMP WITH TIME

ZONE in that when you insert a value into a database column, the values is normalized to the database time zone, and the time-zone displacements is not stored in the column. When you retrieve the value, Oracle returns the value in your local session time zone. INTERVAL YEAR TO MONTH : INTERVAL YEAR[(precision1)] TO MONTH

INTERVAL DAY TO SECOND : INTERVAL DAY[(precision1)] TO SECOND[(precesion2)]. Where

precision1 and precision2 specify the number of digits in the days field and seconds field, respectively. In both cases, you cannot use a symbolic constant or variable to specify the precision; you must use an integer literal in the range 0..9. the defaults are 2 and 6, respectively.

Scalar Variable Declarations

The type %Attribute.

For example: v_v0 table_name%rowtype; v_v1 table_name.colname%type; V_balance number(7,2);

V_min_balance v_balance%type :=10;

A NOT NULL database column constraint does not apply to variables that are declared using %type. Therefore, if you declare a variable using the %TYPE attribute that uses a database column defined as NOT NULL, you can assign the NULL value to the variable.

Declaring Boolean variables

Composite Data Types

Composite data types(also known as collections) are of TABLE,RECORD,NESTED TABLE, and VARRAY types. Use the RECORD data type to treat related but dissimilar data as a logical unit. Use the TABLE data type to reference and manipulate collections of data as whole object. Both RECORD and TABLE data types are covered in detail in a subsequent lesson. NESTED TABLE and VARRAY data types are covered in the Advanced PL/SQL course. 復合數據類型，也被稱作集合。主要包括：表，記錄，嵌入表和數組。 記錄用來處理不同但組合到一起的數據。

表 用來把一個數據集合作為一個整體引用和操作。

記錄和表類型，下面的章節將詳細介紹。嵌入表和數組要看更深一步的 PL/SQL 課程。 For more information, see PL/SQL User’s Gride and reference,”Collections and records.”

LOB Data Type variables Book (CLOB) Photo (BLOB) Movie (BFILE) NCLOB

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