Oracle数据库查询高效分页
Linq提供了Skip和Take的API可以用于分页,由于使用的是Entity Framework,在好奇的驱使下用EFProfiler查看生成的SQL,才知道这样以下分页更好。 主要就是使用了row_numer()over()这样的分析函数,可以直接找到那第5000行开始的地方,然后在取出30行就行
Linq提供了Skip和Take的API可以用于分页,由于使用的是Entity Framework,在好奇的驱使下用EFProfiler查看生成的SQL,才知道这样以下分页更好。 主要就是使用了row_numer()over()这样的分析函数,可以直接找到那第5000行开始的地方,然后在取出30行就行了。
<ol> <li><span><span>select</span><span> * </span></span></li> <li><span> <span>from</span><span> (</span><span>select</span><span> * </span></span></li> <li><span> <span>from</span><span> (</span><span>select</span><span> t.*, </span></span></li> <li><span> row_number() OVER(<span>ORDER</span><span> </span><span>BY</span><span> </span><span>null</span><span>) </span><span>AS</span><span> </span><span>"row_number"</span><span> </span></span></li> <li><span> <span>from</span><span> yz_bingrenyz t) p </span></span></li> <li><span> <span>where</span><span> p.</span><span>"row_number"</span><span> > 5000 </span></span></li> <li><span> ) q </span></li> <li><span> <span>where</span><span> rownum </span></span></li> </ol>
比较分析:
本机测试前者耗时1.3s,后者仅0.25s,从以下的执行计划也能看出差异来。

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

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.

Solutions to Oracle cannot be opened include: 1. Start the database service; 2. Start the listener; 3. Check port conflicts; 4. Set environment variables correctly; 5. Make sure the firewall or antivirus software does not block the connection; 6. Check whether the server is closed; 7. Use RMAN to recover corrupt files; 8. Check whether the TNS service name is correct; 9. Check network connection; 10. Reinstall Oracle software.

MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.

The method to solve the Oracle cursor closure problem includes: explicitly closing the cursor using the CLOSE statement. Declare the cursor in the FOR UPDATE clause so that it automatically closes after the scope is ended. Declare the cursor in the USING clause so that it automatically closes when the associated PL/SQL variable is closed. Use exception handling to ensure that the cursor is closed in any exception situation. Use the connection pool to automatically close the cursor. Disable automatic submission and delay cursor closing.

In Oracle, the FOR LOOP loop can create cursors dynamically. The steps are: 1. Define the cursor type; 2. Create the loop; 3. Create the cursor dynamically; 4. Execute the cursor; 5. Close the cursor. Example: A cursor can be created cycle-by-circuit to display the names and salaries of the top 10 employees.

To stop an Oracle database, perform the following steps: 1. Connect to the database; 2. Shutdown immediately; 3. Shutdown abort completely.

Building a Hadoop Distributed File System (HDFS) on a CentOS system requires multiple steps. This article provides a brief configuration guide. 1. Prepare to install JDK in the early stage: Install JavaDevelopmentKit (JDK) on all nodes, and the version must be compatible with Hadoop. The installation package can be downloaded from the Oracle official website. Environment variable configuration: Edit /etc/profile file, set Java and Hadoop environment variables, so that the system can find the installation path of JDK and Hadoop. 2. Security configuration: SSH password-free login to generate SSH key: Use the ssh-keygen command on each node

SQL statements can be created and executed based on runtime input by using Oracle's dynamic SQL. The steps include: preparing an empty string variable to store dynamically generated SQL statements. Use the EXECUTE IMMEDIATE or PREPARE statement to compile and execute dynamic SQL statements. Use bind variable to pass user input or other dynamic values to dynamic SQL. Use EXECUTE IMMEDIATE or EXECUTE to execute dynamic SQL statements.
