使用 unnest 函数在 Presto 中提取数组元素

Question

I have a requirement around this data where I need to extract array elements but I still want to keep them grouped, which means I can not use unnest function. Below is the sample data:

[ 
  { "emp_id": 8291828, "name": "bruce", }, 
  { "emp_id": 8291823, "name": "Rolli" }
]

My data is in the same format as above,ie (array(row(emp_id varchar, name varchar))) what I need is to get rid of the array, so that data look like

{ "emp_id": 8291828, "name": "bruce", }, 
{ "emp_id": 8291823, "name": "Rolli" }

Would appreciate if anyone can help me on this.

Answer 1

You could use element_at If you have a sequence table (1,2,3, ..).

with numbers as 
(
    select * from 
    (
    Values
    (1),(2),(3)
    ) as x(i)
)
,emp as
(
    select *
    from (
        values
        (ARRAY[cast(ROW(8291828,'bruce') as row(emp_id bigint, name varchar)), cast(row(8291823,'Rolli') as row(emp_id bigint, name varchar))])
    ) as emp (records)
)
select 
element_at(emp.records,i) record
from numbers n
cross join emp
where n.i <= cardinality(emp.records);