ekuiper-new/docs/en_US/sqls/functions/multi_row_functions.md

Multiple Row Functions

A multiple row function is a function that returns multiple rows.

Multiple row function can only be used in the SELECT clause of a query and only allowed 1 multiple rows function in the clause for now.

UNNEST

unnest(array)

The unnest function is used to expand an array into multiple rows. The argument column must be an array. This function will expand the array into multiple rows as a returned result. If the item in the array is map[string]interface object, then it will be built as columns in the result rows.

Examples

Create a stream demo and have below inputs

```json lines { "a": [

1,
2

], "b": 3 }

Rule to get the unnest values:

```text
SQL: SELECT unnest(a) FROM demo
___________________________________________________
{"unnest":1}
{"unnest":2}

Rule to get the unnest values with other columns:

SQL: SELECT unnest(a), b FROM demo
___________________________________________________
{"unnest":1, "b":3}
{"unnest":2, "b":3}

Create a stream demo and have below inputs

```json lines { "x": [

{
  "a": 1,
  "b": 2
},
{
  "a": 3,
  "b": 4
}

], "c": 5 }

Rule to get the unnest values with other columns:

```text
SQL: SELECT unnest(x), c FROM demo
___________________________________________________
{"a":1, "b":2, "c": 5}
{"a":3, "b":4, "c": 5}