Home Database Mysql Tutorial Comprehensive exposure to SQL syntax (1)

Comprehensive exposure to SQL syntax (1)

Dec 24, 2016 pm 05:44 PM
sql syntax

SQL functions and features
In fact, in the previous article, some basic functions of SQL commands have been mentioned. However, through SQL commands, programmers or database administrators (DBA) can:
(1) Create database tables . (Including setting the space that can be used by the table)
  (2) Change the database system environment settings.
  (3) Grant users access rights to a certain database or table.
  (4) Create index values ​​for database tables.
  (5) Modify the database table structure. (Create, delete or modify table fields)
  (6) Create new data in the database.
  (7) Delete data from the database.
  (8) Modify data in the database.
  (9) Query data from the database.
 These are the things that can be accomplished through SQL commands. Doesn’t it seem that there are many more functions than the word “query” represents?

 Classification of SQL syntax

In fact, there are not many SQL commands, but to use SQL to perfection, only a few commands are enough, because SQL commands are grammatical descriptions created for relational databases , so SQL plays a very powerful role in this type of database. The following will classify and introduce the basic SQL syntax commands commonly used in VB. Before explaining the commands and syntax of SQL, SQL is classified below. The types used in SQL syntax can be said to be included in these categories.

 The first category, attribute words (PRedicates)

 It is used in SQL commands to indicate the way to select the records. Such as ALL, TOP and DISTINCT, etc.

  The second category, Declaration

  Make declarations on the name and data type of SQL Parameter or Parameter Query, such as the declaration of PARAMETERS, etc.

 The third category, conditional clause (Clause)

 In SQL queries, some expressions are used to define the conditions of the query to narrow the scope of the search, such as WHERE.

 The fourth category, operator (Operator) and operand (Operation)

 In SQL query, it and Operation together form an expression (Expression), such as BETWEEN....AND operator and INNER JOIN operand.

 The fifth category, Function

  Some common SQL functions, such as AVG(), are functions that find the arithmetic mean.

  The sixth category, SQL statement (Statement)

  The SQL statement can be said to be the main body of SQL grammar. It is used to issue instructions to a specific database and return related data. The syntax structure of SQL is basically It can be represented by the following formula: command + conditional clause

For example:

SELECT*FROM TAB WHERE TAB.NAME='A'

"FROM....WHERE" is a condition Clause, in fact, the syntax of SQL is not difficult. You only need to remember such a rule, and I believe you can quickly understand the usage of SQL.

 SQL syntax and commands


SELECT statement
SELECT[predicate]{*|table.*|[table.]field [,[table.]field2[,...]]} [AS alias1 [,alias2[ ,...]]]
FROM tableexpression [,...][IN externaldatabase]
[WHERE...]
[GROUP BY...]
[HAVING...]
[ORDER BY...]
[WITH OWNERaccess OPTION]
The SELECT statement includes the following parts
predicate



As mentioned earlier, it includes ALL, DISTINCT, DISTINCTROW, and TOP. We can use such statements to limit the results obtained after the query.

  *

 Specify all fields from the specified table.

 table

 The name of the specified table for the fields of the selected records.

 field1,field2

  If the field name you want to read data contains more than one field, the data will be read in the order listed.

 alias1,alias2

  Pseudonyms used to replace the actual field names in the form.

 tableexpression

 Table name or table containing the data we want.

 Externaldatabase

 If a database other than the current one is used, define its name in externaldatabase.
 
  ALL, DISTINCT, DISTINCTROW, TOP attribute word usage

SELECT [ALL|DISTINCT|DISTINCTROW|[TOP n[PERCENT]]] FROM table

  ALL

If you do not specify any field data, the Microsoft Jet database The database engine will select all fields and query the required data set based on the specified conditions.

The above is the content of comprehensive contact with SQL syntax (1). For more related content, please pay attention to the PHP Chinese website (www.php.cn)!


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

Video Face Swap

Video Face Swap

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

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)

Hot Topics

Java Tutorial
1662
14
PHP Tutorial
1262
29
C# Tutorial
1235
24
When might a full table scan be faster than using an index in MySQL? When might a full table scan be faster than using an index in MySQL? Apr 09, 2025 am 12:05 AM

Full table scanning may be faster in MySQL than using indexes. Specific cases include: 1) the data volume is small; 2) when the query returns a large amount of data; 3) when the index column is not highly selective; 4) when the complex query. By analyzing query plans, optimizing indexes, avoiding over-index and regularly maintaining tables, you can make the best choices in practical applications.

Can I install mysql on Windows 7 Can I install mysql on Windows 7 Apr 08, 2025 pm 03:21 PM

Yes, MySQL can be installed on Windows 7, and although Microsoft has stopped supporting Windows 7, MySQL is still compatible with it. However, the following points should be noted during the installation process: Download the MySQL installer for Windows. Select the appropriate version of MySQL (community or enterprise). Select the appropriate installation directory and character set during the installation process. Set the root user password and keep it properly. Connect to the database for testing. Note the compatibility and security issues on Windows 7, and it is recommended to upgrade to a supported operating system.

MySQL: Simple Concepts for Easy Learning MySQL: Simple Concepts for Easy Learning Apr 10, 2025 am 09:29 AM

MySQL is an open source relational database management system. 1) Create database and tables: Use the CREATEDATABASE and CREATETABLE commands. 2) Basic operations: INSERT, UPDATE, DELETE and SELECT. 3) Advanced operations: JOIN, subquery and transaction processing. 4) Debugging skills: Check syntax, data type and permissions. 5) Optimization suggestions: Use indexes, avoid SELECT* and use transactions.

Can mysql and mariadb coexist Can mysql and mariadb coexist Apr 08, 2025 pm 02:27 PM

MySQL and MariaDB can coexist, but need to be configured with caution. The key is to allocate different port numbers and data directories to each database, and adjust parameters such as memory allocation and cache size. Connection pooling, application configuration, and version differences also need to be considered and need to be carefully tested and planned to avoid pitfalls. Running two databases simultaneously can cause performance problems in situations where resources are limited.

Laravel Eloquent ORM in Bangla partial model search) Laravel Eloquent ORM in Bangla partial model search) Apr 08, 2025 pm 02:06 PM

LaravelEloquent Model Retrieval: Easily obtaining database data EloquentORM provides a concise and easy-to-understand way to operate the database. This article will introduce various Eloquent model search techniques in detail to help you obtain data from the database efficiently. 1. Get all records. Use the all() method to get all records in the database table: useApp\Models\Post;$posts=Post::all(); This will return a collection. You can access data using foreach loop or other collection methods: foreach($postsas$post){echo$post->

RDS MySQL integration with Redshift zero ETL RDS MySQL integration with Redshift zero ETL Apr 08, 2025 pm 07:06 PM

Data Integration Simplification: AmazonRDSMySQL and Redshift's zero ETL integration Efficient data integration is at the heart of a data-driven organization. Traditional ETL (extract, convert, load) processes are complex and time-consuming, especially when integrating databases (such as AmazonRDSMySQL) with data warehouses (such as Redshift). However, AWS provides zero ETL integration solutions that have completely changed this situation, providing a simplified, near-real-time solution for data migration from RDSMySQL to Redshift. This article will dive into RDSMySQL zero ETL integration with Redshift, explaining how it works and the advantages it brings to data engineers and developers.

The relationship between mysql user and database The relationship between mysql user and database Apr 08, 2025 pm 07:15 PM

In MySQL database, the relationship between the user and the database is defined by permissions and tables. The user has a username and password to access the database. Permissions are granted through the GRANT command, while the table is created by the CREATE TABLE command. To establish a relationship between a user and a database, you need to create a database, create a user, and then grant permissions.

MySQL: The Ease of Data Management for Beginners MySQL: The Ease of Data Management for Beginners Apr 09, 2025 am 12:07 AM

MySQL is suitable for beginners because it is simple to install, powerful and easy to manage data. 1. Simple installation and configuration, suitable for a variety of operating systems. 2. Support basic operations such as creating databases and tables, inserting, querying, updating and deleting data. 3. Provide advanced functions such as JOIN operations and subqueries. 4. Performance can be improved through indexing, query optimization and table partitioning. 5. Support backup, recovery and security measures to ensure data security and consistency.

See all articles