Home Database Mysql Tutorial 数据库SQL学习的经典案例:学生专业老师分数表的操练

数据库SQL学习的经典案例:学生专业老师分数表的操练

Jun 07, 2016 pm 02:58 PM
sql major Fraction study student database teacher

数据库SQL学习的经典案例:学生专业老师分数表的操练;针对一个问题------选了课程1而没有选课程2的学生有哪些? 下面的SQL语句是各个不同的写法,整理下~ 无 mysql desc SC;+-------+---------------+------+-----+---------+-------+| Field | Type | Null

数据库SQL学习的经典案例:学生专业老师分数表的操练;针对一个问题------选了课程1而没有选课程2的学生有哪些?

下面的SQL语句是各个不同的写法,整理下~
mysql> desc SC;
+-------+---------------+------+-----+---------+-------+
| Field | Type          | Null | Key | Default | Extra |
+-------+---------------+------+-----+---------+-------+
| S_id  | varchar(10)   | YES  |     | NULL    |       |
| C_id  | varchar(10)   | YES  |     | NULL    |       |
| score | decimal(18,1) | YES  |     | NULL    |       |
+-------+---------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> select * from SC;
+------+------+-------+
| S_id | C_id | score |
+------+------+-------+
| 01   | 01   |  80.0 |
| 01   | 02   |  90.0 |
| 01   | 03   |  99.0 |
| 02   | 01   |  70.0 |
| 02   | 02   |  60.0 |
| 02   | 03   |  80.0 |
| 03   | 01   |  80.0 |
| 03   | 02   |  80.0 |
| 03   | 03   |  80.0 |
| 04   | 01   |  50.0 |
| 04   | 02   |  30.0 |
| 04   | 03   |  20.0 |
| 05   | 01   |  76.0 |
| 05   | 02   |  87.0 |
| 06   | 01   |  31.0 |
| 06   | 03   |  34.0 |
| 07   | 02   |  89.0 |
| 07   | 03   |  98.0 |
| 08   | 04   |  79.0 |
| 11   | 03   |  77.9 |
| 12   | 02   |  47.9 |
| 12   | 04   |  47.9 |
| 11   | 01   |  77.9 |
| 01   | 04   |  73.9 |
| 01   | 05   |  83.9 |
| 06   | 04   |  75.0 |
| 06   | 05   |  85.0 |
| 11   | 05   |  81.0 |
| 11   | 04   |  91.0 |
+------+------+-------+
29 rows in set (0.00 sec)


--1
select B.* from SC B where B.C_id = '01' 
and not exists(select * from SC B2 where B.S_id = B2.S_id and B2.C_id = '02');

--2
select * from 
(select B.S_id, B.C_id aC_id, B.score ascore, B2.C_id bC_id, B2.score bscore 
from SC B inner join SC B2 
on B.S_id = B2.S_id and B.C_id = '01' and B2.C_id != '01') 
BBB 
where not exists 
(select * from (select B.S_id, B.C_id aC_id, B.score ascore, B2.C_id bC_id, B2.score bscore 
from SC B inner join SC B2 
on B.S_id = B2.S_id and B.C_id = '01' and B2.C_id != '01') 
CCC where BBB.S_id = CCC.S_id and CCC.bC_id = '02' );

--3
select * from SC where C_id = '01' 
and S_id not in 
(select distinct S_id from SC where C_id = '02');

--4
select B.S_id, B.C_id aC_id, B.score ascore, B2.C_id bC_id, B2.score bscore 
from SC B inner join SC B2 
on B.S_id = B2.S_id and B.C_id = '01' and B2.C_id != '01' 
group by S_id having (aC_id, bC_id) != ('01','02');

--5
select B.*, B2.* from SC B left join SC B2 
on B.S_id = B2.S_id and B2.C_id = '02' 
where B.C_id = '01' and B2.C_id is null;

--6
select B.*, B2.* from SC B right join SC B2 
on B.S_id = B2.S_id and B.C_id = '02' 
where B2.C_id = '01' and B.C_id is null;

--7
select B.S_id, B.C_id aC_id, B.score ascore, B2.C_id bC_id, B2.score bscore 
from SC B inner join SC B2 
on B.S_id = B2.S_id and B.C_id = '01' 
and B2.C_id != '01' 
group by S_id having nullif(bC_id, '02') >> 1;
Copy after login
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)

iOS 18 adds a new 'Recovered' album function to retrieve lost or damaged photos iOS 18 adds a new 'Recovered' album function to retrieve lost or damaged photos Jul 18, 2024 am 05:48 AM

Apple's latest releases of iOS18, iPadOS18 and macOS Sequoia systems have added an important feature to the Photos application, designed to help users easily recover photos and videos lost or damaged due to various reasons. The new feature introduces an album called "Recovered" in the Tools section of the Photos app that will automatically appear when a user has pictures or videos on their device that are not part of their photo library. The emergence of the "Recovered" album provides a solution for photos and videos lost due to database corruption, the camera application not saving to the photo library correctly, or a third-party application managing the photo library. Users only need a few simple steps

Detailed tutorial on establishing a database connection using MySQLi in PHP Detailed tutorial on establishing a database connection using MySQLi in PHP Jun 04, 2024 pm 01:42 PM

How to use MySQLi to establish a database connection in PHP: Include MySQLi extension (require_once) Create connection function (functionconnect_to_db) Call connection function ($conn=connect_to_db()) Execute query ($result=$conn->query()) Close connection ( $conn->close())

How to handle database connection errors in PHP How to handle database connection errors in PHP Jun 05, 2024 pm 02:16 PM

To handle database connection errors in PHP, you can use the following steps: Use mysqli_connect_errno() to obtain the error code. Use mysqli_connect_error() to get the error message. By capturing and logging these error messages, database connection issues can be easily identified and resolved, ensuring the smooth running of your application.

How to connect to remote database using Golang? How to connect to remote database using Golang? Jun 01, 2024 pm 08:31 PM

Through the Go standard library database/sql package, you can connect to remote databases such as MySQL, PostgreSQL or SQLite: create a connection string containing database connection information. Use the sql.Open() function to open a database connection. Perform database operations such as SQL queries and insert operations. Use defer to close the database connection to release resources.

Guangzhou plans to stipulate that primary and secondary schools can prohibit students from bringing mobile phones, and those allowed to bring in should be managed uniformly Guangzhou plans to stipulate that primary and secondary schools can prohibit students from bringing mobile phones, and those allowed to bring in should be managed uniformly Jun 16, 2024 pm 08:00 PM

According to news on June 16, on June 15, the official website and public account of the Guangzhou Municipal People’s Congress posted the “Regulations on the Promotion of Mental Health of Primary and Secondary School Students in Guangzhou (Revised Draft and Draft for Comments)” to solicit opinions and suggestions from all walks of life. Among them, Article 14 of the "Regulations" is titled "Preventing Mobile Phones and Other Intelligent Terminal Products from Entering Campuses" and the specific provisions are as follows: Parents or other guardians of primary and secondary school students should strictly restrict their children's use of mobile phones and other intelligent terminal products. Children of products should regulate the place, time period, duration, frequency, content, functions, permissions and other matters of use, and cooperate with the school to prohibit or restrict students from using mobile phones and other smart terminal products on campus. Schools may prohibit students from bringing mobile phones and other smart terminal products into the school or using them on campus.

How to use database callback functions in Golang? How to use database callback functions in Golang? Jun 03, 2024 pm 02:20 PM

Using the database callback function in Golang can achieve: executing custom code after the specified database operation is completed. Add custom behavior through separate functions without writing additional code. Callback functions are available for insert, update, delete, and query operations. You must use the sql.Exec, sql.QueryRow, or sql.Query function to use the callback function.

How to handle database connections and operations using C++? How to handle database connections and operations using C++? Jun 01, 2024 pm 07:24 PM

Use the DataAccessObjects (DAO) library in C++ to connect and operate the database, including establishing database connections, executing SQL queries, inserting new records and updating existing records. The specific steps are: 1. Include necessary library statements; 2. Open the database file; 3. Create a Recordset object to execute SQL queries or manipulate data; 4. Traverse the results or update records according to specific needs.

PHP connections to different databases: MySQL, PostgreSQL, Oracle and more PHP connections to different databases: MySQL, PostgreSQL, Oracle and more Jun 01, 2024 pm 03:02 PM

PHP database connection guide: MySQL: Install the MySQLi extension and create a connection (servername, username, password, dbname). PostgreSQL: Install the PgSQL extension and create a connection (host, dbname, user, password). Oracle: Install the OracleOCI8 extension and create a connection (servername, username, password). Practical case: Obtain MySQL data, PostgreSQL query, OracleOCI8 update record.

See all articles