延迟加载:即当我们需要用到的时候才进行加载(读取) 当我们希望浏览某条订单信息的时候,才显示其对应的订单详细记录时,我们希望使用延迟加载来实现,这样不仅加快的了读取的效率,同时也避免加载不需要的数据。延迟加载通常用于foreach循环读取数据时。
延迟加载:即当我们需要用到的时候才进行加载(读取)
当我们希望浏览某条订单信息的时候,才显示其对应的订单详细记录时,我们希望使用延迟加载来实现,这样不仅加快的了读取的效率,同时也避免加载不需要的数据。延迟加载通常用于foreach循环读取数据时。
EF中支持延迟加载,是因为 进行查询,返回DbQuery类
为了展示延迟加载,所以 使用 sql server profiler 进行查看 数据的查询。
Sql server profiler 用于监视 sql的连接执行情况。建立一个新的跟踪。
当我们使用DbContext类对EF进行操作时候:
已经执行完查询了,但是 查询跟踪器里面为空:
只有在使用查询结果的时候,EF才会去执行sql语句。
数据库。其实,就是要想对数据库进行操作 直接 对实体 就行操作就行了。
更符合面向对象的思想了。
直接加载的思想:
1、声明变量
2、要查询的条件
3、根据查询条件 去查询 然后 把结果存放在变量中
用的时候,直接把变量拿过来用
延迟加载的思想:
1、声明变量
2、输入要查询的条件
用的时候,把变量和条件 都拿过来,执行完后 在用
两种思想,分别处理不同的情况。就和 真假分页 是一个道理。
1、如果是在foreach循环中加载数据,那么使用延迟加载会比较好,因为不需要一次性将所有数据读取出来,这样虽然有可能会造成n次数据库的查询,但是基本上在可以接受的范围内。
2、如果在开发时就可以预见需要一次性加载所有的数据,包含关联表的所有数据,那么使用使用贪婪加载是比较好的选择,但是此种方式会导致效率问题,特别是数据量大的情况下。

InnoDBBufferPool reduces disk I/O by caching data and indexing pages, improving database performance. Its working principle includes: 1. Data reading: Read data from BufferPool; 2. Data writing: After modifying the data, write to BufferPool and refresh it to disk regularly; 3. Cache management: Use the LRU algorithm to manage cache pages; 4. Reading mechanism: Load adjacent data pages in advance. By sizing the BufferPool and using multiple instances, database performance can be optimized.

Compared with other programming languages, MySQL is mainly used to store and manage data, while other languages such as Python, Java, and C are used for logical processing and application development. MySQL is known for its high performance, scalability and cross-platform support, suitable for data management needs, while other languages have advantages in their respective fields such as data analytics, enterprise applications, and system programming.

MySQL is worth learning because it is a powerful open source database management system suitable for data storage, management and analysis. 1) MySQL is a relational database that uses SQL to operate data and is suitable for structured data management. 2) The SQL language is the key to interacting with MySQL and supports CRUD operations. 3) The working principle of MySQL includes client/server architecture, storage engine and query optimizer. 4) Basic usage includes creating databases and tables, and advanced usage involves joining tables using JOIN. 5) Common errors include syntax errors and permission issues, and debugging skills include checking syntax and using EXPLAIN commands. 6) Performance optimization involves the use of indexes, optimization of SQL statements and regular maintenance of databases.

MySQL is suitable for beginners to learn database skills. 1. Install MySQL server and client tools. 2. Understand basic SQL queries, such as SELECT. 3. Master data operations: create tables, insert, update, and delete data. 4. Learn advanced skills: subquery and window functions. 5. Debugging and optimization: Check syntax, use indexes, avoid SELECT*, and use LIMIT.

MySQL efficiently manages structured data through table structure and SQL query, and implements inter-table relationships through foreign keys. 1. Define the data format and type when creating a table. 2. Use foreign keys to establish relationships between tables. 3. Improve performance through indexing and query optimization. 4. Regularly backup and monitor databases to ensure data security and performance optimization.

MySQL is an open source relational database management system that is widely used in Web development. Its key features include: 1. Supports multiple storage engines, such as InnoDB and MyISAM, suitable for different scenarios; 2. Provides master-slave replication functions to facilitate load balancing and data backup; 3. Improve query efficiency through query optimization and index use.

SQL is used to interact with MySQL database to realize data addition, deletion, modification, inspection and database design. 1) SQL performs data operations through SELECT, INSERT, UPDATE, DELETE statements; 2) Use CREATE, ALTER, DROP statements for database design and management; 3) Complex queries and data analysis are implemented through SQL to improve business decision-making efficiency.

The basic operations of MySQL include creating databases, tables, and using SQL to perform CRUD operations on data. 1. Create a database: CREATEDATABASEmy_first_db; 2. Create a table: CREATETABLEbooks(idINTAUTO_INCREMENTPRIMARYKEY, titleVARCHAR(100)NOTNULL, authorVARCHAR(100)NOTNULL, published_yearINT); 3. Insert data: INSERTINTObooks(title, author, published_year)VA


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

SublimeText3 Chinese version
Chinese version, very easy to use

SublimeText3 English version
Recommended: Win version, supports code prompts!

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool