Column

01 · What is it?

A column is a named attribute that defines one type of data stored for every row in a table.

In a table of customers, for example, customer_id, name, and email can each be columns. Every row has a value for each column, unless the value is allowed to be missing.

02 · Think of it like…

Think of a spreadsheet. A column is one vertical category, such as Name, Email, or Status. The heading tells you what the values below it mean.

customer_id	name	status
101	Ada	active
102	Lin	pending

The headers are columns. Each horizontal line beneath them is a row.

03 · What does it do?

A column gives a table structure and makes its data easier to understand and use.

Names the data

A clear name explains what each stored value represents.

Defines a type

A column can expect text, numbers, dates, identifiers, or another data type.

Supports queries

SQL uses column names to select, filter, sort, and change values.

04 · Where is it used?

Columns appear in every structured table that stores records for an application.

Users

user_id, email, created_at

Orders

order_id, total, order_status

Products

sku, name, price

05 · Example

This table definition creates three named columns with different data types.

CREATE TABLE customers (
  customer_id INTEGER,
  name TEXT,
  email TEXT
);

A query can then choose specific columns instead of returning every value.

SELECT name, email
FROM customers;

06 · How it connects

Table

Column

Row value

SQL query

A table contains columns, each row supplies values for those columns, and SQL works with the named columns.

07 · Do Not Confuse

A named category of data shared by every row in a table.

Row

One complete record containing values across the table’s columns.

Field

A named data item in a record; people often use “field” and “column” interchangeably.

08 · Topic Glossary

ENGLISH TERM	中文	SIMPLE ENGLISH	中文小白理解
Column	列	A named attribute that stores one type of data for every row.	表里每一行都按照同一类别保存数据的一列。
Table	表	A structure that stores related data in rows and columns.	用行和列组织相关数据的结构。
Row	行	One complete record in a table.	表里代表一个对象或事件的一整条记录。
Field	字段	A named piece of information in a record.	一条记录中的某个具体数据项。
Value	值	The actual data stored in a column for one row.	某一行在某一列里真正保存的内容。
Data Type	数据类型	The kind of value a column is designed to store.	规定这一列应该保存文字、数字、日期等哪种数据。
SQL	结构化查询语言	A language used to read and change relational database data.	用来查询和修改关系型数据库数据的语言。
NULL	空值	A special value meaning that data is missing or unknown.	表示数据缺失或未知，不等于数字零或空字符串。

09 · What to Remember

A column names one kind of data in a table.

Every row can provide a value for that column.

SQL uses column names to work with stored data.