What does desc mean in sql

The DESC command in SQL is used to display the schema information of the table, including column names, data types, constraints and default values, which can help users understand the structure of the table. The specific syntax is as follows: DESC table_name;

DESC in SQL

DESC is a keyword in SQL, used to display the schema information of the table, including column names, Data types, constraints and default values. It is an important database operation that helps users understand the structure of tables and find errors in the data.

Syntax

<code class="sql">DESC table_name;</code>

Among them, table_name is the name of the table to query the schema information.

Return results

The DESC command returns a result set containing the following columns:

• Field: Column Name
• Type: The data type of the column
• Null: Whether to allow null values ​​(YES or NO)
• Key: Whether it is a primary key or a foreign key (PRI, MUL or NULL)
• Default: The default value (if any)
• Extra: Other information (such as auto-increment column identification, etc.)

Example

The following example displays the schema information of table customers:

<code class="sql">DESC customers;</code>

The output may look like this:

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

Purpose

The DESC command is useful in the following situations:

• Verify that the schema of the table is as expected
• Identify errors such as data type mismatches or missing constraints
• Understand the default values ​​and limitations of columns in the table
• Help plan database modifications and data loading operations

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