pyspark.sql.functions.string_agg#

pyspark.sql.functions.string_agg(col, delimiter=None)[source]#

Aggregate function: returns the concatenation of non-null input values, separated by the delimiter.

An alias of listagg().

Added in version 4.0.0.

Parameters:

colColumn or column name: target column to compute on.
delimiterColumn, literal string or bytes, optional: the delimiter to separate the values. The default value is None.

Returns:

Column: the column for computed results.

Examples

Example 1: Using string_agg function

>>> from pyspark.sql import functions as sf
>>> df = spark.createDataFrame([('a',), ('b',), (None,), ('c',)], ['strings'])
>>> df.select(sf.string_agg('strings')).show()
+-------------------------+
|string_agg(strings, NULL)|
+-------------------------+
|                      abc|
+-------------------------+

Example 2: Using string_agg function with a delimiter

>>> from pyspark.sql import functions as sf
>>> df = spark.createDataFrame([('a',), ('b',), (None,), ('c',)], ['strings'])
>>> df.select(sf.string_agg('strings', ', ')).show()
+-----------------------+
|string_agg(strings, , )|
+-----------------------+
|                a, b, c|
+-----------------------+

Example 3: Using string_agg function with a binary column and delimiter

>>> from pyspark.sql import functions as sf
>>> df = spark.createDataFrame([(b'',), (b'',), (None,), (b'',)], ['bytes'])
>>> df.select(sf.string_agg('bytes', b'B')).show()
+------------------------+
|string_agg(bytes, X'42')|
+------------------------+
|        [01 42 02 42 03]|
+------------------------+

Example 4: Using string_agg function on a column with all None values

>>> from pyspark.sql import functions as sf
>>> from pyspark.sql.types import StructType, StructField, StringType
>>> schema = StructType([StructField("strings", StringType(), True)])
>>> df = spark.createDataFrame([(None,), (None,), (None,), (None,)], schema=schema)
>>> df.select(sf.string_agg('strings')).show()
+-------------------------+
|string_agg(strings, NULL)|
+-------------------------+
|                     NULL|
+-------------------------+