split column into lines (explode) in dbt with sql - sql

Question

I am very new to dbt, I am trying to explode a column value into rows using SQL on dbt.
I have a table sample_data:
| id | content_toSplit |
| -------- | --------------- |
| 1 | [a, b, c, d] |
| 2 | [a, v] |
| 3 | [m, n, a] |
|id |output_column|
|-----|-------------|
|1 | a |
|1 | b |
|1 | c |
|1 | d |
|2 | a |
|2 | v |
I tried using unnest in a macro, and used the macro in my model:
Macro
{% macro split_column_to_row(column_name) %}
cross join unnest{{ column_name }} as output_column
{% endmacro %}
The Macro used in my model
select id, content_toSplit from {{ref('source')}}
{{split_column_to_row(content_toSplit)}}
But I am getting an "SQL compilation error: Object 'UNNEST' does not exist or not authorized." error. Also, I would like to get a position of each value.
I have also tried the below using SQL:
with unnest_column as (
select
id,
content_toSplit
from my_table, unnest(content_toSplit) as exploded_value
)
select *
from unnest_column
But getting "unexpected '('. syntax error line"

Answer 1

Perhaps your macro is interpreting unnest as a table name since it follows cross join but that is just a guess without the actual generated SQL. Your SQL statement is using unnest improperly. It is uses as an old style (pre SQL-92) cross join. However, no join clause is necessary, just unnest(content_toSplit) as exploded_value in the select column list. (see demo)
select id
, unnest(content_toSplit) as exploded_value
from sample_data
where id < 3; -- needed to get your specific output
Caution: Please be consistent: You initially state I have a table sample_data: yet your SQL references my_table. This is a physically small question, but had it been larger, the inconsistency could actually keep you from getting an answer. Details are important.