Home Backend Development PHP Tutorial Quick Start with SQL Language 1_PHP Tutorial

Quick Start with SQL Language 1_PHP Tutorial

Jul 13, 2016 pm 05:26 PM
language query sql one getting Started fast yes of abbreviation English language


SQL is the abbreviation of English Structured Query Language, which means structured query language. The main function of the SQL language is to establish connections and communicate with various databases. According to ANSI (American National Standards Institute), SQL is used as the standard language for relational database management systems. SQL statements can be used to perform a variety of operations, such as updating data in the database, extracting data from the database, etc. At present, most popular relational database management systems, such as Oracle, Sybase, Microsoft SQL Server, Access, etc., all adopt the SQL language standard. Although many databases have redeveloped and extended SQL statements, standard SQL commands including Select, Insert, Update, Delete, Create, and Drop can still be used to complete almost all database operations. Next, we will introduce the basic knowledge of SQL language in detail.

Database tables
A typical relational database usually consists of one or more objects called tables. All the data or information in the database is saved in these database tables. Each table in the database has its own unique table name, which is composed of rows and columns. Each column includes the column name, data type, and other attributes of the column, and the row specifically contains the information of a certain column. records or data. Below, is an example of a database table named Weather.
The highest and lowest temperature in the city
Beijing 10 5
Shanghai 15 8
Tianjin 8 2
Chongqing 20 13

In this table, "city", "maximum temperature" and "Minimum temperature" is three different columns, and each row in the table contains specific table data.

Data query
Among the many SQL commands, the select statement should be considered the most frequently used. The Select statement is mainly used to query the database and return result data that meets the user's query criteria. The syntax format of the Select statement is as follows:
select column1 [, column2, etc] from tablename
[where condition];
([] indicates optional options)
in the select statement after the select keyword Column names are used to determine which columns will be returned as query results. Users can select any column according to their needs, and can also use the wildcard "*" to set all columns in the returned table.


The table name after the from keyword in the select statement is used to determine the target table for the query operation.
The where optional clause in the Select statement is used to specify which data values ​​or rows will be returned or displayed as query results.
You can use the following operators in the where conditional clause to set query criteria:
= equal to
> greater than
>= greater than or equal to
is not equal to
In addition to the operators mentioned above, the LIKE operator is also very important in the where conditional clause. The LIKE operator is very powerful. By using the LIKE operator, you can select only records with the same format as specified by the user. In addition, we can also use the wildcard "%" to replace any string. For example:
select firstname, lastname, city
from employee
where firstname LIKE 'E%';
(note that the string must be enclosed in single brackets)
The above SQL statement All names starting with E will be searched. Or, use the following statement:
select * from employee
where firstname = ‘May’;
Query all rows named May.

www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/531971.htmlTechArticleSQL is the abbreviation of English Structured Query Language, which means structured query language. The main function of the SQL language is to establish connections and communicate with various databases. According to ANSI (United States...
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

A Diffusion Model Tutorial Worth Your Time, from Purdue University A Diffusion Model Tutorial Worth Your Time, from Purdue University Apr 07, 2024 am 09:01 AM

Diffusion can not only imitate better, but also "create". The diffusion model (DiffusionModel) is an image generation model. Compared with the well-known algorithms such as GAN and VAE in the field of AI, the diffusion model takes a different approach. Its main idea is a process of first adding noise to the image and then gradually denoising it. How to denoise and restore the original image is the core part of the algorithm. The final algorithm is able to generate an image from a random noisy image. In recent years, the phenomenal growth of generative AI has enabled many exciting applications in text-to-image generation, video generation, and more. The basic principle behind these generative tools is the concept of diffusion, a special sampling mechanism that overcomes the limitations of previous methods.

What is the difference between HQL and SQL in Hibernate framework? What is the difference between HQL and SQL in Hibernate framework? Apr 17, 2024 pm 02:57 PM

HQL and SQL are compared in the Hibernate framework: HQL (1. Object-oriented syntax, 2. Database-independent queries, 3. Type safety), while SQL directly operates the database (1. Database-independent standards, 2. Complex executable queries and data manipulation).

Generate PPT with one click! Kimi: Let the 'PPT migrant workers' become popular first Generate PPT with one click! Kimi: Let the 'PPT migrant workers' become popular first Aug 01, 2024 pm 03:28 PM

Kimi: In just one sentence, in just ten seconds, a PPT will be ready. PPT is so annoying! To hold a meeting, you need to have a PPT; to write a weekly report, you need to have a PPT; to make an investment, you need to show a PPT; even when you accuse someone of cheating, you have to send a PPT. College is more like studying a PPT major. You watch PPT in class and do PPT after class. Perhaps, when Dennis Austin invented PPT 37 years ago, he did not expect that one day PPT would become so widespread. Talking about our hard experience of making PPT brings tears to our eyes. "It took three months to make a PPT of more than 20 pages, and I revised it dozens of times. I felt like vomiting when I saw the PPT." "At my peak, I did five PPTs a day, and even my breathing was PPT." If you have an impromptu meeting, you should do it

All CVPR 2024 awards announced! Nearly 10,000 people attended the conference offline, and a Chinese researcher from Google won the best paper award All CVPR 2024 awards announced! Nearly 10,000 people attended the conference offline, and a Chinese researcher from Google won the best paper award Jun 20, 2024 pm 05:43 PM

In the early morning of June 20th, Beijing time, CVPR2024, the top international computer vision conference held in Seattle, officially announced the best paper and other awards. This year, a total of 10 papers won awards, including 2 best papers and 2 best student papers. In addition, there were 2 best paper nominations and 4 best student paper nominations. The top conference in the field of computer vision (CV) is CVPR, which attracts a large number of research institutions and universities every year. According to statistics, a total of 11,532 papers were submitted this year, and 2,719 were accepted, with an acceptance rate of 23.6%. According to Georgia Institute of Technology’s statistical analysis of CVPR2024 data, from the perspective of research topics, the largest number of papers is image and video synthesis and generation (Imageandvideosyn

System76 tips Fedora Cosmic spin for 2025 release with Fedora 42 System76 tips Fedora Cosmic spin for 2025 release with Fedora 42 Aug 01, 2024 pm 09:54 PM

System76 has made waves recently with its Cosmic desktop environment, which is slated to launch with the next major alpha build of Pop!_OS on August 8. However, a recent post on X by System76 CEO, Carl Richell, has tipped that the Cosmic DE developer

A must-read for technical beginners: Analysis of the difficulty levels of C language and Python A must-read for technical beginners: Analysis of the difficulty levels of C language and Python Mar 22, 2024 am 10:21 AM

Title: A must-read for technical beginners: Difficulty analysis of C language and Python, requiring specific code examples In today's digital age, programming technology has become an increasingly important ability. Whether you want to work in fields such as software development, data analysis, artificial intelligence, or just learn programming out of interest, choosing a suitable programming language is the first step. Among many programming languages, C language and Python are two widely used programming languages, each with its own characteristics. This article will analyze the difficulty levels of C language and Python

From bare metal to a large model with 70 billion parameters, here is a tutorial and ready-to-use scripts From bare metal to a large model with 70 billion parameters, here is a tutorial and ready-to-use scripts Jul 24, 2024 pm 08:13 PM

We know that LLM is trained on large-scale computer clusters using massive data. This site has introduced many methods and technologies used to assist and improve the LLM training process. Today, what we want to share is an article that goes deep into the underlying technology and introduces how to turn a bunch of "bare metals" without even an operating system into a computer cluster for training LLM. This article comes from Imbue, an AI startup that strives to achieve general intelligence by understanding how machines think. Of course, turning a bunch of "bare metal" without an operating system into a computer cluster for training LLM is not an easy process, full of exploration and trial and error, but Imbue finally successfully trained an LLM with 70 billion parameters. and in the process accumulate

Counting down the 12 pain points of RAG, NVIDIA senior architect teaches solutions Counting down the 12 pain points of RAG, NVIDIA senior architect teaches solutions Jul 11, 2024 pm 01:53 PM

Retrieval-augmented generation (RAG) is a technique that uses retrieval to boost language models. Specifically, before a language model generates an answer, it retrieves relevant information from an extensive document database and then uses this information to guide the generation process. This technology can greatly improve the accuracy and relevance of content, effectively alleviate the problem of hallucinations, increase the speed of knowledge update, and enhance the traceability of content generation. RAG is undoubtedly one of the most exciting areas of artificial intelligence research. For more details about RAG, please refer to the column article on this site "What are the new developments in RAG, which specializes in making up for the shortcomings of large models?" This review explains it clearly." But RAG is not perfect, and users often encounter some "pain points" when using it. Recently, NVIDIA’s advanced generative AI solution

See all articles