浅谈PDO的rowCount函数
这篇文章主要介绍了浅谈PDO的rowCount函数的相关使用方法和效率问题,需要的朋友可以参考下
PDO有一个函数PDOStatement::rowCount返回上一个SQL语句影响的行数。
rowCount函数对于DELETE, INSERT, 或者UPDATE语句的结果是正确的,但对于select语句则与数据库的实现相关。有些数据库在执行select语句时会将结果集全部读入内存,但对于数量巨大的结果集,这样显然是低效的。大部分的数据库则只会返回结果集的一部分,当需要时再返回其余的结果集,这样无论是内存占用和执行效率都是优化的。对于后一种情况,则rowCount无法返回正确的SELECT语句结果集的行数。 获取正确的SELECT结果的行数有几种方法
1、使用fetchAll函数 $q = $db->query("SELECT ..."); $rows = $q->fetchAll(); $rowCount = count($rows);
2、使用sql count函数 $q = $db->query("SELECT count(*) from db;"); $rows = $q->fetch(); $rowCount = $rows[0];
显然第二种方法更有效率
以上所述就是本文的全部内容了，，希望大家能够喜欢。
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
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
Solution to PHP Fatal error: Call to undefined method PDO::prepare() in
Jun 22, 2023 pm 06:40 PM
PHP is a popular web development language that has been used for a long time. The PDO (PHP Data Object) class integrated in PHP is a common way for us to interact with the database during the development of web applications. However, a problem that some PHP developers often encounter is that when using the PDO class to interact with the database, they receive an error like this: PHPFatalerror:CalltoundefinedmethodPDO::prep
How to use PHP's PDO_PGSQL extension?
Jun 02, 2023 pm 06:10 PM
As a popular programming language, PHP is widely used in the field of web development. Among them, PHP's PDO_PGSQL extension is a commonly used PHP extension. It provides an interactive interface with the PostgreSQL database and can realize data transmission and interaction between PHP and PostgreSQL. This article will introduce in detail how to use PHP's PDO_PGSQL extension. 1. What is the PDO_PGSQL extension? PDO_PGSQL is an extension library of PHP, which
PHP and PDO: How to perform bulk inserts and updates
Jul 28, 2023 pm 07:41 PM
PHP and PDO: How to perform batch inserts and updates Introduction: When using PHP to write database-related applications, you often encounter situations where you need to batch insert and update data. The traditional approach is to use loops to perform multiple database operations, but this method is inefficient. PHP's PDO (PHPDataObject) provides a more efficient way to perform batch insert and update operations. This article will introduce how to use PDO to implement batch insert and update operations. 1. Introduction to PDO: PDO is PH
PHP and PDO: How to handle JSON data in a database
Jul 29, 2023 pm 05:17 PM
PHP and PDO: How to handle JSON data in databases In modern web development, processing and storing large amounts of data is a very important task. With the popularity of mobile applications and cloud computing, more and more data are stored in databases in JSON (JavaScript Object Notation) format. As a commonly used server-side language, PHP's PDO (PHPDataObject) extension provides a convenient way to process and operate databases. Book
PHP and PDO: How to perform paging queries and display data
Jul 29, 2023 pm 04:10 PM
PHP and PDO: How to query and display data in pages When developing web applications, querying and displaying data in pages is a very common requirement. Through paging, we can display a certain amount of data at a time, improving page loading speed and user experience. In PHP, the functions of paging query and display of data can be easily realized using the PHP Data Object (PDO) library. This article will introduce how to use PDO in PHP to query and display data by page, and provide corresponding code examples. 1. Create database and data tables
PHP PDO vs. mysqli: compare and contrast
Feb 19, 2024 pm 12:24 PM
PDOPDO is an object-oriented database access abstraction layer that provides a unified interface for PHP, allowing you to use the same code to interact with different databases (such as Mysql, postgresql, oracle). PDO hides the complexity of underlying database connections and simplifies database operations. Advantages and Disadvantages Advantages: Unified interface, supports multiple databases, simplifies database operations, reduces development difficulty, provides prepared statements, improves security, supports transaction processing Disadvantages: performance may be slightly lower than native extensions, relies on external libraries, may increase overhead, demo code uses PDO Connect to mysql database: $db=newPDO("mysql:host=localhost;dbnam
How to connect to Redis database using PDO
Jul 28, 2023 pm 04:29 PM
How to use PDO to connect to the Redis database. Redis is an open source, high-performance, in-memory storage key-value database that is commonly used in cache, queue and other scenarios. In PHP development, using Redis can effectively improve the performance and stability of applications. Through the PDO (PHPDataObjects) extension, we can connect and operate the Redis database more conveniently. This article will introduce how to use PDO to connect to a Redis database, with code examples. Install the Redis extension at the beginning
PHP and PDO: How to perform database backup and restore operations
Jul 29, 2023 pm 06:54 PM
PHP and PDO: How to perform database backup and restore operations When developing web applications, database backup and restore are very important tasks. As a popular server-side scripting language, PHP provides a wealth of libraries and extensions, among which PDO (PHP Data Objects) is a powerful database access abstraction layer. This article will introduce how to use PHP and PDO to perform database backup and restore operations. Step 1: Connect to the database Before actual operation, we need to establish a connection to the database. Use PDO pair
