A relationship describes how records in one table are logically connected to records in another table.
A relationship describes how records in one table are logically connected to records in another table.
For example, one customer can be connected to many orders. The relationship lets software work with those records as connected parts of one business story.
Simple Definition: A relationship explains which records belong together across tables.
Think of a relationship like a label that connects a person to the things they own.
A customer record does not need to repeat every order detail. Each order keeps its own record, while a shared identifier shows which customer it belongs to.
id · 42
name · Mina
id · 9001
customer_id · 42
A relationship helps a database:
Link related records across tables.
Store shared facts once instead of repeating them.
Combine related data when an application needs it.
Keep links meaningful and valid.
Relationships appear wherever one piece of business data depends on another.
Customers connect to orders.
Authors connect to posts.
Students connect to courses.
Customers connect to tickets.
customers
id | name
42 | Mina
orders
id | customer_id | total
9001| 42 | 49.00SELECT customers.name, orders.total
FROM customers
JOIN orders
ON orders.customer_id = customers.id
WHERE orders.id = 9001;The query follows the relationship to return Mina’s order total.
The relationship is the logical connection; keys and queries are common ways to represent and use it.
The logical connection between related records.
A column that stores a reference to a record in another table.
A SQL operation that reads related rows together.
Relationship = the connection · Foreign key = a stored reference · JOIN = a query operation
| ENGLISH TERM | 中文 | SIMPLE ENGLISH | 中文小白理解 |
|---|---|---|---|
| Relationship | 关系 | A logical connection between records in different tables. | 不同数据表中的记录之间存在的逻辑关联。 |
| Table | 表 | A structure that stores related data in rows and columns. | 用行和列保存相关数据的结构。 |
| Record | 记录 | One complete set of data about an item. | 描述一个对象的一条完整数据。 |
| Primary Key | 主键 | A value that uniquely identifies a record. | 唯一标识一条记录的值。 |
| Foreign Key | 外键 | A column that references a record in another table. | 指向另一张表中记录的字段。 |
| JOIN | 连接查询 | A SQL operation that reads related rows together. | 把相关表中的数据放在一起查询的 SQL 操作。 |
| One-to-Many | 一对多 | One record is connected to many records in another table. | 一条记录可以关联另一张表中的多条记录。 |
A relationship explains how records in different tables belong together.
Keys store references, and SQL queries can use those references to read connected data.
A clear relationship keeps data organized without repeating every fact.