From Wikipedia, the không lấy phí encyclopedia
In the context of a relational database, a row—also called a tuple—represents a single, implicitly structured data item in a table. In simple terms, a database table can be thought of as consisting of rows and columns. Each row in a table represents a phối of related data, and every row in the table has the same structure.
Bạn đang xem: rows là gì
For example, in a table that represents companies, each row would represent a single company. Columns might represent things lượt thích company name, company street address, whether the company is publicly held, its VAT number, etc. In a table that represents the association of employees with departments, each row would associate one employee with one department.
Xem thêm: hence là gì
The implicit structure of a row, and the meaning of the data values in a row, requires that the row be understood as providing a succession of data values, one in each column of the table. The row is then interpreted as a relvar composed of a phối of tuples, with each tuple consisting of the two items: the name of the relevant column and the value this row provides for that column.
Each column expects a data value of a particular type. For example, one column might require a unique identifier, another might require text representing a person's name, another might require an integer representing hourly pay in dollars.
|Column 1||Column 2|
|Row 1||Row 1, Column 1||Row 1, Column 2|
|Row 2||Row 2, Column 1||Row 2, Column 2|
|Row 3||Row 3, Column 1||Row 3, Column 2|
- Column (database)