sqlserver数据库的左右外连接
--左向外联; --如果主表左表中的行没有匹配连接表的行,结果中相关联来自连接表的列显示null; select * from members aleft join orders b on a.M_account=b.M_account 查询结果： liuzc518刘志成1972-05-18男湖南株洲3500.0liuzc518NULLNULLNULLNULLNULLNULL
--左向外联;
--如果主表左表中的行没有匹配连接表的行,结果中相关联来自连接表的列显示null;
select * from members a left join orders b on a.M_account=b.M_account
查询结果：
liuzc518 刘志成 1972-05-18 男 湖南株洲 3500.0 liuzc518 NULL NULL NULL NULL NULL NULL NULL zhao888 赵爱云 1972-02-12 男 湖南株洲 5500.0 zhao888 zhao888 0240810333 2 2005-06-06 00:00:00.000 1 1 0 wangym 王咏梅 1974-08-06 女 湖南长沙 4000.0 wangym0806 wangym 0910810001 1 2005-08-09 00:00:00.000 1 0 0 jinjin 津津有味 1982-04-14 女 北京市 8200.0 jinjin jinjin 0910810004 1 2005-08-09 00:00:00.000 1 1 1 jinjin 津津有味 1982-04-14 女 北京市 8200.0 jinjin jinjin 0910810004 2 2005-06-06 00:00:00.000 1 0 0 lfz 刘法治 1976-08-26 男 天津市 4500.0 lfz0826 lfz 0910810001 1 2005-08-09 00:00:00.000 0 0 0 lfz 刘法治 1976-08-26 男 天津市 4500.0 lfz0826 lfz 0910810004 2 2005-08-09 00:00:00.000 1 1 1 lfz 刘法治 1976-08-26 男 天津市 4500.0 lfz0826 lfz 0910810004 2 2005-06-06 00:00:00.000 1 1 1 zhangzl 张自梁 1975-04-20 男 湖南株洲 4300.0 zhangzl NULL NULL NULL NULL NULL NULL NULL
--右向外联;(与左联接相反)
select * from members a right join orders b on a.M_account=b.M_account
查询结果：
NULL NULL NULL NULL NULL NULL NULL liuzc 0140810324 1 2005-10-09 00:00:00.000 0 0 0 NULL NULL NULL NULL NULL NULL NULL liuzc 0910810004 2 2005-10-09 00:00:00.000 1 1 0 NULL NULL NULL NULL NULL NULL NULL liuzc 0910810001 1 2005-10-09 00:00:00.000 1 1 0 wangym 王咏梅 1974-08-06 女 湖南长沙 4000.0 wangym0806 wangym 0910810001 1 2005-08-09 00:00:00.000 1 0 0 jinjin 津津有味 1982-04-14 女 北京市 8200.0 jinjin jinjin 0910810004 1 2005-08-09 00:00:00.000 1 1 1 lfz 刘法治 1976-08-26 男 天津市 4500.0 lfz0826 lfz 0910810001 1 2005-08-09 00:00:00.000 0 0 0 lfz 刘法治 1976-08-26 男 天津市 4500.0 lfz0826 lfz 0910810004 2 2005-08-09 00:00:00.000 1 1 1 lfz 刘法治 1976-08-26 男 天津市 4500.0 lfz0826 lfz 0910810004 2 2005-06-06 00:00:00.000 1 1 1 jinjin 津津有味 1982-04-14 女 北京市 8200.0 jinjin jinjin 0910810004 2 2005-06-06 00:00:00.000 1 0 0 zhao888 赵爱云 1972-02-12 男 湖南株洲 5500.0 zhao888 zhao888 0240810333 2 2005-06-06 00:00:00.000 1 1 0
--全外连接;
全外连接是左联接和右连接的结合，返回左表和右表中所有的行;如果行在另一个表中没有匹配,另一个表中的select子语句
的列显示的为null,反之，结果中的整个行包含两个表的数据值
select * from members a full join orders b on a.M_account=b.M_account
查询结果：
liuzc518 刘志成 1972-05-18 男 湖南株洲 3500.0 liuzc518 NULL NULL NULL NULL NULL NULL NULL zhao888 赵爱云 1972-02-12 男 湖南株洲 5500.0 zhao888 zhao888 0240810333 2 2005-06-06 00:00:00.000 1 1 0 wangym 王咏梅 1974-08-06 女 湖南长沙 4000.0 wangym0806 wangym 0910810001 1 2005-08-09 00:00:00.000 1 0 0 jinjin 津津有味 1982-04-14 女 北京市 8200.0 jinjin jinjin 0910810004 1 2005-08-09 00:00:00.000 1 1 1 jinjin 津津有味 1982-04-14 女 北京市 8200.0 jinjin jinjin 0910810004 2 2005-06-06 00:00:00.000 1 0 0 lfz 刘法治 1976-08-26 男 天津市 4500.0 lfz0826 lfz 0910810001 1 2005-08-09 00:00:00.000 0 0 0 lfz 刘法治 1976-08-26 男 天津市 4500.0 lfz0826 lfz 0910810004 2 2005-08-09 00:00:00.000 1 1 1 lfz 刘法治 1976-08-26 男 天津市 4500.0 lfz0826 lfz 0910810004 2 2005-06-06 00:00:00.000 1 1 1 zhangzl 张自梁 1975-04-20 男 湖南株洲 4300.0 zhangzl NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL liuzc 0140810324 1 2005-10-09 00:00:00.000 0 0 0 NULL NULL NULL NULL NULL NULL NULL liuzc 0910810004 2 2005-10-09 00:00:00.000 1 1 0 NULL NULL NULL NULL NULL NULL NULL liuzc 0910810001 1 2005-10-09 00:00:00.000 1 1 0
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
1664
14
1422
52
1316
25
1267
29
1239
24
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
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
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 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 save JSON data to database in Golang?
Jun 06, 2024 am 11:24 AM
JSON data can be saved into a MySQL database by using the gjson library or the json.Unmarshal function. The gjson library provides convenience methods to parse JSON fields, and the json.Unmarshal function requires a target type pointer to unmarshal JSON data. Both methods require preparing SQL statements and performing insert operations to persist the data into the database.
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.
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.
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.
