帮忙写条简单的sql
a表 b表 c表 ，a表和b表条件关联gid ,b表和c表关联cid，我要怎么把这3个表联表呀？
条件是gid=20
数据库类型：mysql
回复讨论(解决方案)
select * from b left join(a,c) on (a.gid=b.gid and c.cid=b.cid) where b.gid=20
如果不想要可能出现的 NULL，则
select * from a,b,c where a.gid=b.gid and b.cid=c.cid and a,gid=20
你安装一个Navicat，建立一个视图，完全不需要手写了。 直接拖就行。
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
1666
14
1425
52
1327
25
1273
29
1253
24
The easiest way to query the hard drive serial number
Feb 26, 2024 pm 02:24 PM
The hard disk serial number is an important identifier of the hard disk and is usually used to uniquely identify the hard disk and identify the hardware. In some cases, we may need to query the hard drive serial number, such as when installing an operating system, finding the correct device driver, or performing hard drive repairs. This article will introduce some simple methods to help you check the hard drive serial number. Method 1: Use Windows Command Prompt to open the command prompt. In Windows system, press Win+R keys, enter "cmd" and press Enter key to open the command
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).
Usage of division operation in Oracle SQL
Mar 10, 2024 pm 03:06 PM
"Usage of Division Operation in OracleSQL" In OracleSQL, division operation is one of the common mathematical operations. During data query and processing, division operations can help us calculate the ratio between fields or derive the logical relationship between specific values. This article will introduce the usage of division operation in OracleSQL and provide specific code examples. 1. Two ways of division operations in OracleSQL In OracleSQL, division operations can be performed in two different ways.
Comparison and differences of SQL syntax between Oracle and DB2
Mar 11, 2024 pm 12:09 PM
Oracle and DB2 are two commonly used relational database management systems, each of which has its own unique SQL syntax and characteristics. This article will compare and differ between the SQL syntax of Oracle and DB2, and provide specific code examples. Database connection In Oracle, use the following statement to connect to the database: CONNECTusername/password@database. In DB2, the statement to connect to the database is as follows: CONNECTTOdataba
Detailed explanation of the Set tag function in MyBatis dynamic SQL tags
Feb 26, 2024 pm 07:48 PM
Interpretation of MyBatis dynamic SQL tags: Detailed explanation of Set tag usage MyBatis is an excellent persistence layer framework. It provides a wealth of dynamic SQL tags and can flexibly construct database operation statements. Among them, the Set tag is used to generate the SET clause in the UPDATE statement, which is very commonly used in update operations. This article will explain in detail the usage of the Set tag in MyBatis and demonstrate its functionality through specific code examples. What is Set tag Set tag is used in MyBati
What does the identity attribute in SQL mean?
Feb 19, 2024 am 11:24 AM
What is Identity in SQL? Specific code examples are needed. In SQL, Identity is a special data type used to generate auto-incrementing numbers. It is often used to uniquely identify each row of data in a table. The Identity column is often used in conjunction with the primary key column to ensure that each record has a unique identifier. This article will detail how to use Identity and some practical code examples. The basic way to use Identity is to use Identit when creating a table.
How to write a simple student performance report generator using Java?
Nov 03, 2023 pm 02:57 PM
How to write a simple student performance report generator using Java? Student Performance Report Generator is a tool that helps teachers or educators quickly generate student performance reports. This article will introduce how to use Java to write a simple student performance report generator. First, we need to define the student object and student grade object. The student object contains basic information such as the student's name and student number, while the student score object contains information such as the student's subject scores and average grade. The following is the definition of a simple student object: public
How to solve the 5120 error in SQL
Mar 06, 2024 pm 04:33 PM
Solution: 1. Check whether the logged-in user has sufficient permissions to access or operate the database, and ensure that the user has the correct permissions; 2. Check whether the account of the SQL Server service has permission to access the specified file or folder, and ensure that the account Have sufficient permissions to read and write the file or folder; 3. Check whether the specified database file has been opened or locked by other processes, try to close or release the file, and rerun the query; 4. Try as administrator Run Management Studio as etc.
