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ARRAY_MAP
Applies to ✅ Open Source Edition ✅ Express Edition ✅ Professional Edition ✅ Enterprise Edition
The ARRAY_MAP function allows for mapping array elements of an array to another value.
A few SQL dialects, including ClickHouse, DuckDB, and Trino have introduced higher order functions with a lambda syntax to help implement features like this one. jOOQ can map a Java lambda to a SQL lambda, and emulate the feature using standard SQL functionality (using UNNEST and ARRAY_AGG) if the function isn't available.
SELECT array_map(ARRAY[1, 2, 2, 3], e -> square(e))
create.select(arrayMap(array(1, 2, 2, 3), DSL::square)).fetch();
The result would look like this:
+----------------+ | array_map | +----------------+ | [ 1, 4, 4, 9 ] | +----------------+
Dialect support
This example using jOOQ:
arrayMap(array(1, 2, 2, 3), DSL::square)
Translates to the following dialect specific expressions:
Aurora Postgres, Postgres
(
SELECT coalesce(
array_agg((e * e)),
CAST(ARRAY[] AS int[])
)
FROM UNNEST(ARRAY[1, 2, 2, 3]) t (e)
)
BigQuery
(
SELECT coalesce(
array_agg((e * e)),
CAST(ARRAY[] AS Array<int64>)
)
FROM (
SELECT null e
FROM UNNEST([STRUCT(1 AS dual)]) AS dual
WHERE FALSE
UNION ALL
SELECT *
FROM UNNEST(ARRAY[1, 2, 2, 3]) t
) t
)
ClickHouse
arrayMap( e -> (e * e), ARRAY(1, 2, 2, 3) )
CockroachDB
(
SELECT coalesce(
array_agg((e * e)),
CAST(ARRAY[] AS int4[])
)
FROM UNNEST(ARRAY[1, 2, 2, 3]) t (e)
)
DuckDB
array_transform( ARRAY[1, 2, 2, 3], e -> (e * e) )
H2, HSQLDB
(
SELECT coalesce(
array_agg((e * e)),
CAST(ARRAY[] AS int array)
)
FROM UNNEST(ARRAY[1, 2, 2, 3]) t (e)
)
Trino
transform( ARRAY[1, 2, 2, 3], e -> (e * e) )
ASE, Access, Aurora MySQL, DB2, Derby, Exasol, Firebird, Hana, Informix, MariaDB, MemSQL, MySQL, Oracle, Redshift, SQLDataWarehouse, SQLServer, SQLite, Snowflake, Sybase, Teradata, Vertica, YugabyteDB
/* UNSUPPORTED */
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