DESCRIBE QUERYDESCRIBE QUERY
返回查询输出的元数据。Returns the metadata of output of a query.
语法Syntax
{ DESC | DESCRIBE } [ QUERY ] input_statement
参数Parameters
QUERY 此子句是可选的,并可以省略。QUERY This clause is optional and may be omitted.
input_statementinput_statement
生成语句的结果集,可以是以下内容之一:A result set producing statement and may be one of the following:
SELECT
语句aSELECT
statementCTE(Common table expression)
语句aCTE(Common table expression)
statementINLINE TABLE
语句anINLINE TABLE
statementTABLE
语句aTABLE
statementFROM
语句aFROM
statement`
有关查询参数的详细语法,请参阅 select-statement。Refer to select-statement for a detailed syntax of the query parameter.
示例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 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|
+--------+---------+----------+