Snowflake - is it possible to "merge" array output to table query - snowflake-cloud-data-platform

Question

i have two inputs:
a. Table A with 3 columns: a ,b , c - with 7 rows
b. Table B with an array column d , the array has 7 values.
Is there a way to "merge" the table A and TABLE B in a query - so that the first row of A and the first cell value of B will printed in the same row ?
Input:
For example:
Table A- Column 1
a
b
c
Table A- Column 2
d
e
f
Table b - column 1 (and only)
k
r
j
OUTPUT
should be three columns:
two first columns : column a, b (from table a)
third column - which is column 1 from table 2

Answer 1

You can use Flatten to convert your array into a table. Then you just need to define ordering and how to join them together.
Here's an example, where I use a ROW_NUMBER() to provide an ordering. And since I added it to both tableA and the flattened tableB, it can also be used to join the records together.
If you have IDs for ordering or joining, then that might be slightly cleaner, but with the simple columns provided in the example, you need to do something like this to line up the array values to the table rows.
with tA as (
select col1, col2,
ROW_NUMBER() OVER(ORDER BY col1) rnum
from tableA
)
,tB as (
select
x.value::string col1,
ROW_NUMBER() OVER(ORDER BY 1) rnum
from tableB ,
lateral flatten(input => array) x
)
SELECT a.col1, a.col2, b.col1
FROM tA a
JOIN tB b
ON a.rnum = b.rnum;

Answer 2

There is no "first row" in databases. There is a first with respect to an order you place on the data. Thus there a number of way to get just the "first row" of table A and table B.
On is to only select the first rows, I will use CTE but it can be done in a sub-select also. Via a QUALIFY and ROW_NUMBER, and to make it 'stable' I will use the selected output column. After that to JOIN the two tables, I will use a CROSS-JOIN, but given there are only one row from both CTE's this will give just one output row. But this does not feel like what you want.
WITH first_from_table_a AS (
SELECT column1, column2
FROM table_a
QUALIFY ROW_NUMBER() OVER (ORDER BY column1) = 1
), first_from_table_b AS (
SELECT column1
FROM table_b
QUALIFY ROW_NUMBER() OVER (ORDER BY column1) = 1
)
SELECT a.column1, a.column2, b.column1
FROM first_from_table_a AS a
CROSS JOIN first_from_table_b AS b
The problem with this is, if there are other things you are want to do this over it doesn't scale.
FIRST_VALUE is a function that could also help, if you join your data on some other schema, and want to chose a value from a larger set, but really the problem needs to be clarified more.
Another way to consider your question is to use the same ROW_NUMBER idea, and join on those, thus:
WITH first_from_table_a AS (
SELECT column1,
column2,
ROW_NUMBER() OVER (ORDER BY column1) AS rn
FROM table_a
), first_from_table_b AS (
SELECT column1,
ROW_NUMBER() OVER (ORDER BY column1) AS rn
FROM table_b
)
SELECT a.column1, a.column2, b.column1
FROM first_from_table_a AS a
JOIN first_from_table_b AS b
ON a.rn = b.rn
ORDER BY a.rn