DESCRIBE QUERY
說明
DESCRIBE QUERY 陳述式用於傳回查詢輸出的元資料。可以使用簡寫 DESC 取代 DESCRIBE 來描述查詢輸出。
語法
{ DESC | DESCRIBE } [ QUERY ] input_statement
參數
-
QUERY 此子句是選用的，可以省略。
-
input_statement
指定產生結果集的陳述式，可以是下列其中之一
SELECT陳述式CTE(Common table expression)陳述式INLINE TABLE陳述式TABLE陳述式FROM陳述式
請參閱 select-statement，以取得查詢參數的詳細語法。
範例
-- 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 an 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| Agecolumn|
| 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| Agecolumn|
+--------+---------+----------+