DESCRIBE QUERY

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

  1. { 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

  1. -- Create table `person`
  2. CREATE TABLE person (name STRING , age INT COMMENT 'Age column', address STRING);
  4. -- Returns column metadata information for a simple select query
  5. DESCRIBE QUERY SELECT age, sum(age) FROM person GROUP BY age;
  6. +--------+---------+----------+
  7. |col_name|data_type|   comment|
  8. +--------+---------+----------+
  9. |     age|      int|Age column|
  10. |sum(age)|   bigint|      null|
  11. +--------+---------+----------+
  13. -- Returns column metadata information for common table expression (`CTE`).
  14. DESCRIBE QUERY WITH all_names_cte
  15.     AS (SELECT name from person) SELECT * FROM all_names_cte;
  16. +--------+---------+-------+
  17. |col_name|data_type|comment|
  18. +--------+---------+-------+
  19. |    name|   string|   null|
  20. +--------+---------+-------+
  22. -- Returns column metadata information for an inline table.
  23. DESC QUERY VALUES(100, 'John', 10000.20D) AS employee(id, name, salary);
  24. +--------+---------+-------+
  25. |col_name|data_type|comment|
  26. +--------+---------+-------+
  27. |      id|      int|   null|
  28. |    name|   string|   null|
  29. |  salary|   double|   null|
  30. +--------+---------+-------+
  32. -- Returns column metadata information for `TABLE` statement.
  33. DESC QUERY TABLE person;
  34. +--------+---------+----------+
  35. |col_name|data_type|   comment|
  36. +--------+---------+----------+
  37. |    name|   string|      null|
  38. |     age|      int| Agecolumn|
  39. | address|   string|      null|
  40. +--------+---------+----------+
  42. -- Returns column metadata information for a `FROM` statement.
  43. -- `QUERY` clause is optional and can be omitted.
  44. DESCRIBE FROM person SELECT age;
  45. +--------+---------+----------+
  46. |col_name|data_type|   comment|
  47. +--------+---------+----------+
  48. |     age|      int| Agecolumn|
  49. +--------+---------+----------+