What does desc mean in mysql?

In MySQL, the "desc" command is used to display the structural information of the table, including field name, data type, length or precision, whether it is empty, default value, and key type (primary key, foreign key, or index) .

Meaning in MySQL

In the MySQL database management system, "desc" is a command, used To display the structure information of the table. Specifically, the "desc" command provides the following information:

• Field Name: The name of each field of the table.
• Data type: The data type stored in each field (for example, INT, VARCHAR, DATE, etc.).
• Length or precision: For character type fields, the maximum length is displayed; for numeric type fields, the precision and decimal places are displayed.
• Is it empty: Indicates whether the field allows empty values ​​(YES/NO).
• Default value: The default value of the field (if present).
• Key: Indicates whether the field is a primary key, a foreign key, or part of an index (if applicable).

Usage

The syntax of the "desc" command is as follows:

DESC table_name;

where "table_name" is the table whose structural information you want to view name.

Example

Suppose you have a table named "customers" with the following structure:

<code>CREATE TABLE customers (
    id INT NOT NULL AUTO_INCREMENT,
    name VARCHAR(255) NOT NULL,
    email VARCHAR(255) UNIQUE NOT NULL,
    phone VARCHAR(20) NULL,
    PRIMARY KEY (id)
);</code>

To view the structure information of this table, You can run the following command:

DESC customers;

The output is as follows:

<code>Field           Type             Null    Key     Default  Extra
id              int               NO      PRI     NULL    auto_increment
name            varchar(255)     NO      MUL     NULL
email           varchar(255)     NO      UNI     NULL
phone           varchar(20)      YES     MUL     NULL</code>

The output shows the four fields of the "customers" table: id, name, email, and phone. It also provides information about each field's data type, whether it is empty, key type, and default value.

The above is the detailed content of What does desc mean in mysql?. For more information, please follow other related articles on the PHP Chinese website!