Relational Database Service

We feel that no matter what kind of system we are working on, we have to be more or less connected to the database. Now we are talking about the database, of course, it is a relational database. So what is a relational database service (RDB? In a relational database, data is stored in rows and columns for your understanding. These rows and columns are called tables, and a group of tables form a database.

We feel that no matter what kind of system we are working on, we have to be more or less connected to the database. Now we are talking about the database, of course, it is a relational database. So what is a relational database service (RDB? In a relational database, data is stored in rows and columns for your understanding. These rows and columns are called tables, and a group of tables form a database.

We feel that no matter what kind of system we are working on, we have to be more or less connected to the database. Now we are talking about the database, of course, it is a relational database. So what is a relational database service (RDB?

In a relational database, data is stored in rows and columns for your understanding. These rows and columns are called tables, and a group of tables form a database. In relational databases: data items are organized by relationships. relationship is a connection between tables. Through relationships, we can flexibly represent and manipulate data. In addition, you can easily use Query to retrieve data in the database. A Query is a SELECT statement used to specify the row and column of the database.

Relational databases usually contain the following components: Client, Server, and Database ).

Relational databases are database systems that support relational models. In the real world, the relationships between entities and entities are expressed by relational models. A relational model consists of three parts: relational data structure, relational operation set, and Relational integrity constraint. A relational model consists of three parts: relational data structure, relational operation set, and integrity constraint. Relational operations include relational algebra, relational calculus, relational algebra, and relational calculus ). Integrity constraints provide a wide range of Integrity: entity integrity, referential integrity, and user-defined integrity.

Based on the degree of relationships supported by relational systems, relational systems can be divided into four categories: Table-based systems, (minimal) relational systems, fully-relational systems, and fully-relational systems. Table System: Only relational data structures (tables) are supported, and set-level operations are not supported. (Minimal) relational system: supports relational data structures. It supports relational data structures, selection, projection, and connection operations. Relational systems, such systems support relational data structures and all relational algebra operations (functionally equivalent to relational algebra)