DESCRIBE
Description
This statement is used to display the schema information of the specified table.
Syntax
DESC[RIBE] [<ctl_name>.][<db_name>.]<table_name> [ALL];
Required Parameters
1.<table_name>
Specifies the identifier (i.e., name) of the table, which must be unique within its database.
The identifier must start with a letter character (or any language character if Unicode name support is enabled), and cannot contain spaces or special characters, unless the entire identifier string is enclosed in backticks (e.g.,
My Object).The identifier cannot use reserved keywords.
For more details, please refer to identifier requirements and reserved keywords.
Optional Parameters
1.<ctl_name>.<db_name>
Specifies the identifier (i.e., name) of the data catalog and database.
The identifier must start with a letter character (or any language character if Unicode name support is enabled), and cannot contain spaces or special characters, unless the entire identifier string is enclosed in backticks (e.g.,
My Database).The identifier cannot use reserved keywords.
For more details, please refer to identifier requirements and reserved keywords.
2.ALL
Only valid for internal tables. Returns all Index information of internal tables.
Return Value
When ALL is not specified, the return value is as follows:
| Column | Description |
|---|---|
| Field | Column name |
| Type | Data type |
| Null | Whether NULL values are allowed |
| Key | Whether it's a key column |
| Default | Default value |
| Extra | Displays some additional information |
In version 3.0.7, a new session variable show_column_comment_in_describe was added. When set to true, an additional Comment column will be added to display column comment information.
When ALL is specified, for internal tables, the return value is as follows:
| Column | Description |
|---|---|
| IndexName | Table name |
| IndexKeysType | Table model |
| Field | Column name |
| Type | Data type |
| Null | Whether NULL values are allowed |
| Key | Whether it's a key column |
| Default | Default value |
| Extra | Displays some additional information |
| Visible | Whether it's visible |
| DefineExpr | Definition expression |
| WhereClause | Filter condition related definitions |
Permission Control
Users executing this SQL command must have at least the following permissions:
| Permission (Privilege) | Object | Notes |
|---|---|---|
| SELECT_PRIV | Table | When executing DESC, you need to have SELECT_PRIV permission on the queried table |
Examples
- Display Base Table Schema
DESC test_table;
+---------+-------------+------+-------+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-------+---------+-------+
| user_id | bigint | No | true | NULL | |
| name | varchar(20) | Yes | false | NULL | NONE |
| age | int | Yes | false | NULL | NONE |
+---------+-------------+------+-------+---------+-------+
