What Is a Database Schema?

The database structure refers to the structure of the associated structured data set reasonably stored on the storage device of the computer. A database structure contains various components, including databases, data tables, fields, filters, and so on.

Database structure

Database

The database used in Visual Basic is a relational database. A database consists of one or a set of data tables. Each database is stored on disk as a file, which corresponds to a physical file. Different databases correspond to physical files in different ways. For dBASE, FoxPro and Paradox database, a data table is a separate database file, while for Microsoft Access, Btrieve format database, a database file can contain multiple data tables.

Data Table

Referred to as a table, it is composed of a set of data records. The data in the database is organized in tables. A table is a related set of data arranged in rows; each table contains the same type of information. The table is actually a two-dimensional table. For example, the test results of all students in a class can be stored in a table. Each row in the table corresponds to a student. This row includes the student's student number, name, and the results of each course.

Record

Each row in the table is called a record, and it consists of several fields.

Field

Also called domain. Each column in the table is called a field. Each field has corresponding description information, such as data type, data width, and so on.

Index

To improve the efficiency of accessing the database, you can use indexes on the database. When the database is large, in order to find the specified record, the efficiency of using and not using an index is very different. An index is actually a special type of table that contains the values of key fields (defined by the user) and pointers to the actual record locations. These values and pointers are stored in a specific order (also defined by the user), so that Find the required data records at a faster speed.

Query

An SQL (Structured Query Language) command used to obtain a specified set of records from one or more tables or perform a specified operation on a table. When reading data from a database, it is often desired that the data read out meets certain conditions and can be sorted by a certain field. Using SQL, this can be done easily and more efficiently. SQL is a non-procedural language (some people call it the fourth generation language). When you use it to find a specified record, you only need to indicate what to do, not how to do it. Each statement can be regarded as a query. According to this query, the required query results can be obtained.

Filter

A filter is a component of the database. It combines indexing and sorting to set conditions and then output the required data according to the given conditions.

View

The view of data refers to the number of records found (or processed) and the order in which these records are displayed (or processed). In general, views are controlled by filters and indexes. ^[1]