What does column mean in mysql?

Column (column) is an attribute in a database table used to store specific values ​​for each row. Features include unique names, data types, lengths, nullability, and foreign keys. Column is the basic building block of data structure, storage, retrieval, relationship building and operation, and is specified through the CREATE TABLE statement.

Column in MySQL

What is Column?

Column, also known as column, is an attribute or data item in a database table. It represents a specific value for each row of data in the table.

Characteristics of Column

• Name: Each Column has a unique name that identifies it.
• Data type: The type of data stored in the Column, such as INTEGER, VARCHAR or DATE.
• Length: For some data types (such as VARCHAR), Column has a value that specifies its maximum length.
• Allow null values: Column can be set to allow null values ​​(NULL), or prohibit null values ​​(NOT NULL).
• Default value: When no value is specified, Column can be automatically filled with a default value.
• Foreign key: Column can be specified as a foreign key to associate rows in a table with rows in another table.

Purpose of Column

Column is the basic building block for storing, retrieving, and manipulating data. They are used to:

• Define data structures in tables
• Store and retrieve specific values ​​
• Establish data relationships between tables
• Execution Query, sort and filter operations

Create Column

When creating a table, use the CREATE TABLE statement to specify the name, data type and optionality of each Column Attributes. For example:

<code class="sql">CREATE TABLE users (
  id INT NOT NULL AUTO_INCREMENT,
  name VARCHAR(255) NOT NULL,
  email VARCHAR(255) UNIQUE NOT NULL
);</code>

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