Postgres-11 : Alter Table dynamically - postgresql

Question

I am trying to alter table based on another table dynamically.
Below is the piece of code i wrote in postgresql stored procedure.
But running out into some syntax errors.
Please help me here.
I just started working in postgresql and i am from sql server background. Like how we do in sql server print stmts do debug dynamic queries inside procedures; do we have any link to refer please share that as well. It would help me.
DROP TABLE IF EXISTS temp_table;
CREATE TEMP TABLE temp_table AS
with cte as
(
select column_name,data_type,character_maximum_length
from information_schema."columns" c
where table_name = 'customer_new' and table_schema = 'public'
and column_default is null
)
,cte1 as
(
select column_name,data_type,character_maximum_length
from information_schema."columns" c
where table_name = 'customer_old' and table_schema = 'public'
and column_default is null
)
select cte.column_name,
case when cte.character_maximum_length is not null then cte.data_type||'('||cte.character_maximum_length||')' else cte.data_type end as data_type
from cte
left join cte1 on cte.column_name = cte1.column_name
where cte1.column_name is null;
for v_column_name,v_data_type in SELECT column_name,data_type FROM temp_table
loop
execute format ('alter table %s add column %s %s ;', v_dump_table_name, v_column_name, v_data_type);
end loop;
DROP TABLE IF EXISTS temp_table;
Thanks in advance.

Answer 1

DROP TABLE IF EXISTS temp_table;
CREATE TEMP TABLE temp_table AS
with cte as
(
select column_name,data_type,character_maximum_length
from information_schema."columns" c
where table_name = 'customer_new' and table_schema = 'public'
and column_default is null
)
,cte1 as
(
select column_name,data_type,character_maximum_length
from information_schema."columns" c
where table_name = 'customer_old' and table_schema = 'public'
and column_default is null
)
select 'alter table '||v_dump_table_name||' add column '||cte2.column_name||' '||data_type
as col
from cte2;
for v_column in SELECT col FROM temp_table
loop
execute format ('%s ;', v_column);
end loop;
DROP TABLE IF EXISTS temp_table;