chunguangtang-CSDN博客

原创 oracle对大对象类型操作：blob，clob，nclob，bfile

3-4 Lob类型 13.4.1 基本介绍 Oracle和plsql都支持lob(large object) 类型，用来存储大数量数据，如图像文件，声音文件等。Oracle 9i realse2支持存储最大为4g的数据，oracle 10g realse1支持最大8到128万亿字节的数据存储，依赖于你的db的block size。在plsql中可以申明的lob类型的变量如下：类型描述BFILE 二进制文件,存储在数据库外的操作系统文件

2010-11-02 21:28:00 1419

原创 Basic Elements of Oracle SQL 之 Comments

Comments You can associate comments with SQL statements and schema objects. Comments Within SQL Statements Comments within SQL statements do not affect the statement execution, but they may make your application easier for you to read

2010-10-14 16:03:00 790

原创 Basic Elements of Oracle SQL 之 Pseudocolumns

PseudocolumnsA pseudocolumn behaves like a table column, but is not actually stored in the table. You can select from pseudocolumns, but you cannot insert, update, or delete their values. This section describes these pseudocolumns:CURRVAL and NEXTVALA sequ

2010-10-14 15:59:00 633

原创 Basic Elements of Oracle SQL 之 Nulls

NullsIf a column in a row has no value, then the column is said to be null, or to contain null. Nulls can appear in columns of any datatype that are not restricted by NOT NULL or PRIMARY KEY integrity constraints. Use a null when the actual value is not

2010-10-14 14:58:00 576

原创 Basic Elements of Oracle SQL 之 Literals

Literals The terms literal and constant value are synonymous and refer to a fixed data value. For example, 'JACK', 'BLUE ISLAND', and '101' are all character literals; 5001 is a numeric literal. Character literals are enclosed in single quotatio

2010-10-14 14:54:00 854

原创 Miscellaneous Single-Row Functions

Miscellaneous Single-Row FunctionsThe following single-row functions do not fall into any of the other single-row function categories:DECODEPurposeDECODE compares expr to each search value one by one. If expr is equal to a search, then Oracle returns the c

2010-10-12 14:48:00 635

原创 Conversion Functions

Conversion FunctionsConversion functions convert a value from one datatype to another. Generally, the form of the function names follows the convention datatypeTOdatatype. The first datatype is the input datatype. The second datatype is the output datatype

2010-10-12 14:38:00 547

原创 Datetime Functions

Datetime FunctionsDatetime functions operate on values of the DATE datatype. All datetime functions return a datetime or interval value of DATE datatype, except the MONTHS_BETWEEN function, which returns a number. The datetime functions are:ADD_MONTHSPurpo

2010-10-12 13:33:00 412

原创记一次纠结了我3天的oracle 问题的解决

自己机器上装了oracle,平时写的系统都是连到上面.前天突然连不上去了,jdbc连oracle总是报错,但是我通过pl/sql是可以的.抛一大堆错,懒的贴上来,网上有很多人遇到过这个问题,大都是说java连接oracle的代码写的有问题.然而,我系统用了很久了,一直好好的.而且最近从来没改过,而且我也不会白痴到犯那些低级错误,连jdbc连接oracle的代码也写错.检查了甚至有几十遍之后,还是觉得想不通,甚至重装了oracle,几乎都绝望了,然而还是无解.这几天吃不好,睡不好,反反复复老在想这件事情,因为

2010-09-02 18:30:00 963 2

原创 Oracle通用日志表设计

-- Create sequence create sequence SEQ_COMMON_LOGminvalue 1maxvalue 999999999999999999999999999start with 1increment by 1cache 20;-- Create tablecreate table TU_COMMON_LOG( COL_SEQUENCE NUMBER(20) not null, COL_DATE DATE not null,

2010-08-30 10:35:00 4311

原创 Oracle Character Functions

Character Functions Returning Character Values Character functions that return character values return values of the same datatype as the input argument.Functions that return CHAR values are limited in length to 2000 bytes. Functions that return

2010-08-27 17:15:00 950

原创 Oracle Number Functions

Number Functions Number functions accept numeric input and return numeric values. Most of these functions return values that are accurate to 38 decimal digits. The transcendental functions COS, COSH, EXP, LN, LOG, SIN, SINH, SQRT, TAN, and TANH

2010-08-27 14:48:00 566

原创 Oracle Functions

Functions Functions are similar to operators in that they manipulate data items and return a result. Functions differ from operators in the format of their arguments. This format enables them to operate on zero, one, two, or more arguments:<br /

2010-08-27 13:23:00 1606

原创 Oracle Conditions

Conditions A condition specifies a combination of one or more expressions and logical (Boolean) operators and returns a value of TRUE, FALSE, or unknown This chapter contains the following sections:About SQL ConditionsComparison

2010-08-24 13:04:00 1391

原创 Oracle Expression Lists

An expression list is a combination of other expressions. Expression lists can appear in comparison and membership conditions and in GROUPBY clauses of queries and subqueries. Comparison and membership conditions appear in the

2010-08-18 16:07:00 575

原创 Oracle Operators

An operator manipulates individual data items and returns a result. This chapter contains these sections:About SQL OperatorsArithmetic OperatorsConcatenation OperatorSet OperatorsUser-Defined Operators This chapter discusses non

2010-08-18 14:46:00 1119

原创 Key Technologies Primer

Key Technologies Primer "The time has come," the Walrus said, "To talk of many things: Of shoes -- and ships -- and sealing-wax -- Of cabbages -- and kings -- And why the sea is boiling hot -- And whether pigs have wings." The Usual Suspects<br

2010-08-15 10:08:00 734

原创 crud

CRUD是指在做计算处理时的增加(Create)、查询(Retrieve)（重新得到数据）、更新(Update)和删除(Delete)几个单词的首字母简写。主要被用在描述软件系统中数据库或者持久层的基本操作功能。 　　In computing, CRUD is an acronym for create, retrieve, update, and delete. It is used to refer to the basic functions of a database or

2010-08-14 14:08:00 417

原创 Hibernate

Hibernate是一个开放源代码的对象关系映射框架，它对JDBC进行了非常轻量级的对象封装，使得Java程序员可以随心所欲的使用对象编程思维来操纵数据库。 Hibernate可以应用在任何使用JDBC的场合，既可以在Java的客户端程序使用，也可以在Servlet/JSP的Web应用中使用，最具革命意义的是，Hibernate可以在应用EJB的J2EE架构中取代CMP，完成数据持久化的重任。 [编辑本段]核心接口简介　　Hibernate的核心接口一共有5个，分别为:Session、Ses

2010-08-14 13:09:00 582

原创 POJO

POJO（Plain Old Java Objects）简单的Java对象，实际就是普通JavaBeans，是为了避免和EJB混淆所创造的简称。 在Java应用程序中的角色使用POJO名称是为了避免和EJB混淆起来, 而且简称比较直接. 其中有一些属性及其getter setter方法的类,有时可以作为value object或dto(Data Transform Object)来使用.当然,如果你有一个简单的运算属性也是可以的,但不允许有业务方法,也不能携带有connection之类的方法

2010-08-14 12:24:00 456

原创 Handling PL/SQL Errors

Predefined PL/SQL ExceptionsAn internal exception is raised implicitly whenever your PL/SQL program violates an Oracle rule or exceeds a system-dependent limit. Every Oracle error has a number, but exceptions must be handled by name. So, PL/SQL predefines

2010-08-03 17:37:00 724

原创 oracle TIMESTAMP datatype

The TIMESTAMP datatype is an extension of the DATE datatype. It stores the year, month, and day of the DATE datatype, plus hour, minute, and second values. This datatype is useful for storing precise time values. Specify the TIMESTAMP datatype as fol

2010-08-02 16:39:00 722

转载 oracle analytic functions

OLAP函数语法的总结 ORACLE OLAP 函数 最近这个东东用得特别多，总结了一下。 语法: FUNCTION_NAME(,,...) OVER () OLAP函数语法四个部分: 1、function本身用于对窗口中的数据进行操作； 2、partitioning clause 用于将结果集分区； 3、order by clause 用于对

2010-07-23 16:15:00 556

原创 oracle hierarchical query

Hierarchical Queries If a table contains hierarchical data, then you can select rows in a hierarchical order using the hierarchical query clause: Text description of hierarchical_query_clause： [START WITH condition] CONNECT BY conditio

2010-07-21 14:13:00 1592

原创 oracle sql loader

1. 首先创建bat文件 my_bat.bat内容格式为sqlldr userid=用户名/密码@数据库 control=控制文件下面参数可以不带，指定log文件log=ld.logbad=ld_bad.logdiscard=ld_dis.log例如sqlldr userid=produsr/prod_123@ffv2dev2 control=my_control.txt2. 控制文件中自带数据my_control.txt内容为：LOAD DATA INFILE * append

2010-07-21 11:00:00 470

原创 oracle materialized view

物化视图，它是用于预先计算并保存表连接或聚集等耗时较多的操作的结果，这样，在执行查询时，就可以避免进行这些耗时的操作，而从快速的得到结果。物化视图有很多方面和索引很相似：使用物化视图的目的是为了提高查询性能；物化视图对应用透明，增加和删除物化视图不会影响应用程序中SQL 语句的正确性和有效性；物化视图需要占用存储空间；当基表发生变化时，物化视图也应当刷新。　　其中物化视图有三种：聚集物化视图、包含连接物化视图、嵌套物化视图。但三种物化视图的快速刷新的限制条件有很大区别，而其他方面则区别不大。创建物化视图时

2010-07-19 10:49:00 1331

原创最小生成树

概述　　1、最小生成树　　对于连通的带权图(连通网)G，其生成树也是带权的。生成树T各边的权值总和称为该树的权，记作：　　这里: 　　TE表示T的边集　　w(u，v)表示边(u，v)的权。　　权最小的生成树称为G的最小生成树(Minimum Spanning Tree)。最小生成树可简记为MST。应用　　生成树和最小生成树有许多重要的应用。　　【例】网络G表示n各城市之间的通信线路网线路（其中顶点表示城市，边表示两个城市之间的通信线路，边上的权值表示线路的长度或造价）。可通过求该网络的最小生成

2010-06-14 15:59:00 676

原创 What Is SQL?

What Is SQL? SQL (pronounced as the letters S-Q-L or as sequel) is an abbreviation for Structured Query Language. SQL is a language designed specifically for communicating with databases. Unlike other languages (spoken languages like English, or

2010-06-01 16:27:00 587

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