[SPARK-27444][SQL][FOLLOWUP][MINOR][TEST] Add a test for describing multi select query.

## What changes were proposed in this pull request?
This is a minor pr to add a test to describe a multi select query.

## How was this patch tested?
Added a test in describe-query.sql

Closes apache#24370 from dilipbiswal/describe-query-multiselect-test.

Authored-by: Dilip Biswal <[email protected]>
Signed-off-by: Wenchen Fan <[email protected]>

Author: dilipbiswal

sql/core/src/main/scala/org/apache/spark/sql/execution/command/tables.scala

@@ -635,7 +635,9 @@ case class DescribeTableCommand(
  * 3. VALUES statement.
  * 4. TABLE statement. Example : TABLE table_name
  * 5. statements of the form 'FROM table SELECT *'
- * 6. Common table expressions (CTEs)
+ * 6. Multi select statements of the following form:
+ *    select * from (from a select * select *)
+ * 7. Common table expressions (CTEs)
  */
 case class DescribeQueryCommand(query: LogicalPlan)
   extends DescribeCommandBase {

sql/core/src/test/resources/sql-tests/inputs/describe-query.sql

@@ -10,11 +10,11 @@ DESC SELECT 10.00D as col1;
 DESC QUERY SELECT key FROM desc_temp1 UNION ALL select CAST(1 AS DOUBLE);
 DESC QUERY VALUES(1.00D, 'hello') as tab1(col1, col2);
 DESC QUERY FROM desc_temp1 a SELECT *;
-
-
--- Error cases.
 DESC WITH s AS (SELECT 'hello' as col1) SELECT * FROM s;
 DESCRIBE QUERY WITH s AS (SELECT * from desc_temp1) SELECT * FROM s;
+DESCRIBE SELECT * FROM (FROM desc_temp2 select * select *);
+
+-- Error cases.
 DESCRIBE INSERT INTO desc_temp1 values (1, 'val1');
 DESCRIBE INSERT INTO desc_temp1 SELECT * FROM desc_temp2;
 DESCRIBE

sql/core/src/test/resources/sql-tests/results/describe-query.sql.out

@@ -1,5 +1,5 @@
 -- Automatically generated by SQLQueryTestSuite
--- Number of queries: 16
+-- Number of queries: 17
 
 
 -- !query 0
@@ -97,10 +97,19 @@ val                 	string
 
 
 -- !query 11
-DESCRIBE INSERT INTO desc_temp1 values (1, 'val1')
+DESCRIBE SELECT * FROM (FROM desc_temp2 select * select *)
 -- !query 11 schema
-struct<>
+struct<col_name:string,data_type:string,comment:string>
 -- !query 11 output
+key                 	int                 	                    
+val                 	string
+
+
+-- !query 12
+DESCRIBE INSERT INTO desc_temp1 values (1, 'val1')
+-- !query 12 schema
+struct<>
+-- !query 12 output
 org.apache.spark.sql.catalyst.parser.ParseException
 
 mismatched input 'desc_temp1' expecting {<EOF>, '.'}(line 1, pos 21)
@@ -110,11 +119,11 @@ DESCRIBE INSERT INTO desc_temp1 values (1, 'val1')
 ---------------------^^^
 
 
--- !query 12
+-- !query 13
 DESCRIBE INSERT INTO desc_temp1 SELECT * FROM desc_temp2
--- !query 12 schema
+-- !query 13 schema
 struct<>
--- !query 12 output
+-- !query 13 output
 org.apache.spark.sql.catalyst.parser.ParseException
 
 mismatched input 'desc_temp1' expecting {<EOF>, '.'}(line 1, pos 21)
@@ -124,14 +133,14 @@ DESCRIBE INSERT INTO desc_temp1 SELECT * FROM desc_temp2
 ---------------------^^^
 
 
--- !query 13
+-- !query 14
 DESCRIBE
    FROM desc_temp1 a
      insert into desc_temp1 select *
      insert into desc_temp2 select *
--- !query 13 schema
+-- !query 14 schema
 struct<>
--- !query 13 output
+-- !query 14 output
 org.apache.spark.sql.catalyst.parser.ParseException
 
 mismatched input 'insert' expecting {<EOF>, '(', ',', 'ANTI', 'CLUSTER', 'CROSS', 'DISTRIBUTE', 'EXCEPT', 'FULL', 'GROUP', 'HAVING', 'INNER', 'INTERSECT', 'JOIN', 'LATERAL', 'LEFT', 'LIMIT', 'NATURAL', 'ORDER', 'PIVOT', 'RIGHT', 'SELECT', 'SEMI', 'MINUS', 'SORT', 'UNION', 'WHERE', 'WINDOW'}(line 3, pos 5)
@@ -144,17 +153,17 @@ DESCRIBE
      insert into desc_temp2 select *
 
 
--- !query 14
+-- !query 15
 DROP TABLE desc_temp1
--- !query 14 schema
+-- !query 15 schema
 struct<>
--- !query 14 output
+-- !query 15 output
 
 
 
--- !query 15
+-- !query 16
 DROP TABLE desc_temp2
--- !query 15 schema
+-- !query 16 schema
 struct<>
--- !query 15 output
+-- !query 16 output