DESCRIBE QUERY

2020-01-21

Description

The DESCRIBE QUERY statement is used to return the metadata of output of a query. A shorthand DESC may be used instead of DESCRIBE to describe the query output.

Syntax

{ DESC | DESCRIBE } [ QUERY ] input_statement

Parameters

QUERY
This clause is optional and may be omitted.
input_statement
Specifies a result set producing statement and may be one of the following:
  • a SELECT statement
  • a CTE(Common table expression) statement
  • an INLINE TABLE statement
  • a TABLE statement
  • a FROM statement
Please refer to select-statement for a detailed syntax of the query parameter.

Examples

-- Create table person CREATE TABLE person (name STRING , age INT COMMENT 'Age column', address STRING);

-- Returns column metadata information for a simple select query DESCRIBE QUERY select age, sum(age) FROM person GROUP BY age; +--------+---------+----------+ |col_name|data_type|comment | +--------+---------+----------+ |age |int |Age column| |sum(age)|bigint |null | +--------+---------+----------+

-- Returns column metadata information for common table expression (CTE). DESCRIBE QUERY WITH all_names_cte AS (SELECT name from person) SELECT * FROM all_names_cte; +--------+---------+-------+ |col_name|data_type|comment| +--------+---------+-------+ |name |string |null | +--------+---------+-------+

-- Returns column metadata information for a inline table. DESC QUERY VALUES(100, 'John', 10000.20D) AS employee(id, name, salary); +--------+---------+-------+ |col_name|data_type|comment| +--------+---------+-------+ |id |int |null | |name |string |null | |salary |double |null | +--------+---------+-------+

-- Returns column metadata information for TABLE statement. DESC QUERY TABLE person; +--------+---------+----------+ |col_name|data_type|comment | +--------+---------+----------+ |name |string |null | |age |int |Age column| |address |string |null | +--------+---------+----------+

-- Returns column metadata information for a FROM statement. -- QUERY clause is optional and can be omitted. DESCRIBE FROM person SELECT age; +--------+---------+----------+ |col_name|data_type|comment | +--------+---------+----------+ |age |int |Age column| +--------+---------+----------+