schema | 易学教程

How to query the metadata of indexes in PostgreSQL

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问题 I need to be able to query a PostgreSQL database to obtain information about the indexes present and their details. On SQL Server, I can do the following to get a list of all tables/indexes/columns for all indexes: select TABLE_NAME, INDEX_NAME, NON_UNIQUE, COLUMN_NAME from INFORMATION_SCHEMA.STATISTICS where TABLE_SCHEMA = 'my_schema' order by TABLE_NAME, INDEX_NAME, SEQ_IN_INDEX It seems that the STATISTICS table of INFORMATION_SCHEMA is a SQL Server extension. How can I do the equivalent

How to query the metadata of indexes in PostgreSQL

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Spring MVC

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SpringMVC框架图 SpringMVC接口解释 DispatcherServlet接口： spring 提供的前端控制器，所有的请求都有经过它来统一分发。在DispatcherServlet将请求分发给Spring Controller之前，需要借助于Spring提供的HandlerMapping定位到具体的Controller。 HandlerMapping接口：能够完成客户请求到Controller映射。 Controller接口：需要为并发用户处理上述请求，因此实现Controller接口时，必须保证线程安全并且可重用。Controller将处理用户请求，这和Struts Action扮演的角色是一致的。一旦Controller处理完用户请求，则返回ModelAndView对象给DispatcherServlet前端控制器，ModelAndView中包含了模型（Model）和视图（View）。从宏观角度考虑，DispatcherServlet是整个Web应用的控制器；从微观考虑，Controller是单个Http请求处理过程中的控制器，而ModelAndView是Http请求过程中返回的模型（Model）和视图（View）。 ViewResolver接口： Spring提供的视图解析器（ViewResolver）在Web应用中查找View对象

SpringMVC框架图解析

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Spring框架提供了构造Web应用程序的全能MVC模块。Spring MVC分离了控制器、模型对象、分派器以及处理程序对象的角色，这种分离让它们更容易进行制定。是一个标准的MVC框架。那你猜一猜哪一部分应该是哪一部分？ SpringMVC框架图 SpringMVC接口解释 DispatcherServlet接口： Spring提供的前端控制器，所有的请求都有经过它来统一分发。在DispatcherServlet将请求分发给Spring Controller之前，需要借助于Spring提供的HandlerMapping定位到具体的Controller。 HandlerMapping接口：能够完成客户请求到Controller映射。 Controller接口：需要为并发用户处理上述请求，因此实现Controller接口时，必须保证线程安全并且可重用。Controller将处理用户请求，这和Struts Action扮演的角色是一致的。一旦Controller处理完用户请求，则返回ModelAndView对象给DispatcherServlet前端控制器，ModelAndView中包含了模型（Model）和视图（View）。从宏观角度考虑，DispatcherServlet是整个Web应用的控制器；从微观考虑，Controller是单个Http请求处理过程中的控制器

spring-datesource.xml配置，spring集成mybatis

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搭建spring应用项目时，如果持久层使用iBatis框架的话，需要集成mybatis。下面粘贴出spring-mybatis.xml的配置文件 <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd http://www.springframework.org/schema/aop http:

xml schema construct for elements to occur any number of times in any order

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问题 i wanna write an xml schema that can accept some elements that can occur any number of times in any order. like following examples. it should satisfy all similar combination. lease help me and thanks in advance. Example 1 <root> <node1> one </node1> <node1> two </node1> <node2> three </node2> <node1> four </node1> <node2> five </node2> <node2> six </node2> </root> Example 2 <root> <node1> one </node1> <node2> two </node2> <node1> three </node1> <node2> four </node2> <node2> five </node2>

Represent an optional attribute as a C++ class member

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问题 I am generating C++ code based on a schema. There are entities and each entity contain attribute(s) with each attribute having a corresponding data type. Now the problem is some of these attributes are "optional", meaning that they do not have to be part of the class declaration. However, in C++, something is either a member of class or not a member of class, there is no concept such as "optional data member". Entities will be the class names, and attributes will be the class members. I am

Update database schema in Entity Framework

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问题 I installed VS SP1 and played around with Entity Framework. I created a schema from an existing database and tried some basic operations. Most of it went well, except the database schema update. I changed the database in every basic way: added a new table deleted a table added a new column to an existing table deleted a column from an existing table changed the type of an existing column The first three went well, but the type change and the column deletion did not followed the database

Oracle 同义词

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比较简单，直接摘录自https://www.cnblogs.com/lijiaman/p/6629227.html (一)同义词的概念同义词是数据库中表、视图、索引或其他模式对象的别名，与视图相似，同义词不占用实际的存储空间，在数据字典中只存同义词的定义。在开发数据库时，应尽量避免直接引用表、视图或其他数据库对象，否则，当表的结构发生了改变，就会影响应用程序的使用，这个时候需要重新编译程序，如果为数据库对象创建了同义词，就可以在程序中使用同义词，这样表的结构发生变化，也不会影响到应用程序。此外，运用同义词还可以隐藏数据库对象名称以及对象所有者的信息，还可以简化对数据库对象的访问。（二）同义词分类同义词分为私有同义词和公有同义词，私有同义词只能被创建他的用户拥有，该用户可以控制其他用户对其同义词的使用权。公有同义词被用户组PUBLIC所拥有，数据库所有用户都可以使用共有同义词。（三）同义词相关权限（1）系统权限： SYSTEM PRIVILEGE MARK CREATE SYNONYM 在当前Schema中创建私有同义词。同时可以修改、删除同义词 CREATE PUBLIC SYNONYM 在当前 Schema中创建公有同义词 CREATE ANY SYNONYM 在任意Schema中创建私有同义词 DROP ANY SYNONYM

Perl, LibXML and Schemas

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问题 I have an example Perl script which I am trying to load and validate a file against a schema, them interrogate various nodes. #!/usr/bin/env perl use strict; use warnings; use XML::LibXML; my $filename = 'source.xml'; my $xml_schema = XML::LibXML::Schema->new(location=>'library.xsd'); my $parser = XML::LibXML->new (); my $doc = $parser->parse_file ($filename); eval { $xml_schema->validate ($doc); }; if ($@) { print "File failed validation: $@" if $@; } eval { print "Here\n"; foreach my $book

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