explode
table-valued generator function
Applies to: Databricks SQL Databricks Runtime
Returns a set of rows by un-nesting collection
.
In Databricks SQL and Databricks Runtime 13.3 LTS and above this function supports named parameter invocation.
explode(collection)
collection
: AnARRAY
orMAP
expression.
A set of rows composed of the elements of the array or the keys and values of the map.
The column produced by explode
of an array is named col
.
The columns for a map are called key
and value
.
If collection
is NULL
no rows are produced. To return a single row with NULL
s for the array or map values use the explode_outer() function.
Applies to: Databricks Runtime 12.1 and earlier:
explode
can only be placed in theSELECT
list as the root of an expression or following a LATERAL VIEW. When placing the function in theSELECT
list there must be no other generator function in the sameSELECT
list or UNSUPPORTED_GENERATOR.MULTI_GENERATOR is raised.Applies to: Databricks SQL Databricks Runtime 12.2 LTS and above:
Invocation from the LATERAL VIEW clause or the
SELECT
list is deprecated. Instead, invokeexplode
as a table_reference.
Applies to: Databricks SQL Databricks Runtime 12.1 and earlier:
> SELECT explode(array(10, 20)) AS elem, 'Spark';
10 Spark
20 Spark
> SELECT explode(map(1, 'a', 2, 'b')) AS (num, val), 'Spark';
1 a Spark
2 b Spark
> SELECT explode(array(1, 2)), explode(array(3, 4));
Error: UNSUPPORTED_GENERATOR.MULTI_GENERATOR
-- The difference between explode() and explode_outer() is that explode_outer() returns NULL if the array is NULL.
> SELECT explode_outer(c1) AS elem, 'Spark' FROM VALUES(array(10, 20)), (null) AS T(c1);
10 Spark
20 Spark
NULL Spark
> SELECT explode(c1) AS elem, 'Spark' FROM VALUES(array(10, 20)), (null) AS T(c1);
10 Spark
20 Spark
Applies to: Databricks SQL Databricks Runtime 12.2 LTS and above:
> SELECT elem, 'Spark' FROM explode(array(10, 20)) AS t(elem);
10 Spark
20 Spark
> SELECT num, val, 'Spark' FROM explode(map(1, 'a', 2, 'b')) AS t(num, val);
1 a Spark
2 b Spark
> SELECT * FROM explode(array(1, 2)), explode(array(3, 4));
1 3
1 4
2 3
2 4
-- Using lateral correlation in Databricks 12.2 and above
> SELECT * FROM explode(array(1, 2)) AS t, LATERAL explode(array(3 * t.col, 4 * t.col));
1 3
1 4
2 6
2 8