DESC

Description

You can use the statement to perform the following operations:

View the schema of a table stored in your CelerData cluster, along with the type of the sort key and materialized view of the table.

Syntax

DESC[RIBE] [db_name.]table_name [ALL];

Parameters

Parameter	Required	Description
db_name	No	The database name.
table_name	Yes	The table name.
ALL	No	If this keyword is specified, you can view the type of the sort key, materialized view, and schema of a table stored in your CelerData cluster. If this keyword is not specified, you only view the table schema.

Output

+-----------+---------------+-------+------+------+-----+---------+-------+
| IndexName | IndexKeysType | Field | Type | Null | Key | Default | Extra |
+-----------+---------------+-------+------+------+-----+---------+-------+

The following table describes the parameters returned by this statement.

Parameter	Description
IndexName	The table name.
IndexKeysType	The type of the sort key of the table.
Field	The column name.
Type	The data type of the column.
Null	Whether the column values can be NULL. `yes`: indicates the values can be NULL. `no`: indicates the values cannot be NULL.
Key	Whether the column is used as the sort key. `true`: indicates the column is used as the sort key. `false`: indicates the column is not used as the sort key.
Default	The default value for the data type of the column. If the data type does not have a default value, a NULL returned.
Extra	This field displays the following information about the column: The aggregate function used by the column, such as `SUM` and `MIN`. Whether a bloom filter index is created on the column. If so, the value of `Extra` is `BLOOM_FILTER`.

Note: For information about how a materialized view is displayed in the output, see Example 2.

Examples

Example 1: View the schema of example_table stored in your CelerData cluster.

DESC example_table;

DESC default_catalog.example_db.example_table;

The output of the preceding statements is as follows.

+-------+---------------+------+-------+---------+-------+
| Field | Type          | Null | Key   | Default | Extra |
+-------+---------------+------+-------+---------+-------+
| k1    | TINYINT       | Yes  | true  | NULL    |       |
| k2    | DECIMAL(10,2) | Yes  | true  | 10.5    |       |
| k3    | CHAR(10)      | Yes  | false | NULL    |       |
| v1    | INT           | Yes  | false | NULL    |       |
+-------+---------------+------+-------+---------+-------+

Example 2: View the schema, type of the sort key, and materialized view of sales_records stored in your CelerData cluster. In the following example, one materialized view store_amt is created based on sales_records.

DESC db1.sales_records ALL;

+---------------+---------------+-----------+--------+------+-------+---------+-------+
| IndexName     | IndexKeysType | Field     | Type   | Null | Key   | Default | Extra |
+---------------+---------------+-----------+--------+------+-------+---------+-------+
| sales_records | DUP_KEYS      | record_id | INT    | Yes  | true  | NULL    |       |
|               |               | seller_id | INT    | Yes  | true  | NULL    |       |
|               |               | store_id  | INT    | Yes  | true  | NULL    |       |
|               |               | sale_date | DATE   | Yes  | false | NULL    | NONE  |
|               |               | sale_amt  | BIGINT | Yes  | false | NULL    | NONE  |
|               |               |           |        |      |       |         |       |
| store_amt     | AGG_KEYS      | store_id  | INT    | Yes  | true  | NULL    |       |
|               |               | sale_amt  | BIGINT | Yes  | false | NULL    | SUM   |
+---------------+---------------+-----------+--------+------+-------+---------+-------+

Example 3: View the schema of hive_table stored in your Hive cluster.

DESC hive_catalog.hive_db.hive_table;

+-------+----------------+------+-------+---------+---------------+ 
| Field | Type           | Null | Key   | Default | Extra         | 
+-------+----------------+------+-------+---------+---------------+ 
| id    | INT            | Yes  | false | NULL    |               | 
| name  | VARCHAR(65533) | Yes  | false | NULL    |               | 
| date  | DATE           | Yes  | false | NULL    | partition key | 
+-------+----------------+------+-------+---------+---------------+