A relational database organizes structured data into tables and connects those tables through relationships.
A relational database stores structured data in tables and uses shared fields to connect related records across those tables.
Each table usually represents one kind of thing, such as users, orders, or products. Rows hold records, columns describe fields, and keys make connections explicit.
Think of it like a set of spreadsheets with carefully managed links.
One sheet lists customers, another lists orders, and an order keeps the customer ID that points back to the right customer. The link avoids copying the same customer details into every order.
One row per customer.
id · name · emailOne row per order.
id · customer_id · totalA relational database helps software keep structured data consistent and useful.
Keep related data in clear tables.
Link records with keys and relationships.
Find combined answers with SQL.
Enforce rules with constraints and transactions.
Relational databases are common when an application needs reliable records, clear links, and repeatable queries.
Customers, carts, orders, and payments.
Accounts, transfers, balances, and audit records.
Patients, appointments, clinicians, and results.
Inventory, suppliers, tickets, and schedules.
A customer places an order, and the database keeps the order connected to the customer without duplicating the customer record.
SELECT customers.name, orders.total
FROM customers
JOIN orders ON orders.customer_id = customers.id;The application sends a request, backend logic creates a SQL query, and the relational database returns structured results.
Stores tables and manages relationships, rules, and transactions.
Expresses queries and data changes for relational databases.
Software that runs and controls database storage, access, and operations.
| ENGLISH TERM | 中文 | SIMPLE ENGLISH | 中文小白理解 |
|---|---|---|---|
| Relational Database | 关系型数据库 | A database that stores data in tables and connects related records. | 把数据放在表里，并把相关记录连接起来的数据库。 |
| Table | 表 | A structure that stores one kind of data in rows and columns. | 按行和列保存某一类数据的结构。 |
| Row | 行 | One complete record in a table. | 表中的一条完整记录。 |
| Column | 列 | One named type of information in a table. | 表中一种有名字的数据类型。 |
| Primary Key | 主键 | A value that uniquely identifies a row. | 唯一标识一行数据的值。 |
| Foreign Key | 外键 | A field that points to a row in another table. | 指向另一张表中某条记录的字段。 |
| Relationship | 关系 | A connection between records in different tables. | 不同表中记录之间的关联。 |
| Join | 连接 | A SQL operation that combines related rows from tables. | 用 SQL 把相关表中的数据合并起来查看。 |
| Constraint | 约束 | A rule that protects the validity of stored data. | 保证保存的数据符合规则的限制。 |
| Transaction | 事务 | A group of operations treated as one unit. | 作为一个整体执行的一组数据库操作。 |
Relational databases organize structured data into tables.
Keys connect related records, and SQL works across those relationships.
Constraints and transactions help keep data reliable as applications change it.