How to execute result of a query in PostgreSQL - sql

Question

I am trying to create a view by joining two tables. These two tables have a few columns with the same name. Which gives an error
SQL Error [42701]: ERROR: column "column_name" specified more than once
I cannot use column names while creating the view as there are 30+ columns and new columns will be added to both tables over the period of time. Hence, I have to use * to get all the columns.
Now, to eliminate columns which exist in both the table, I went ahead and did this:
SELECT 'SELECT ' || STRING_AGG('u2.' || column_name, ', ') || ' FROM schema_name.table_name u2'
FROM information_schema.columns
WHERE table_name = 'table_name'
AND table_schema = 'schema_name'
AND column_name NOT IN ('column_name');
This gives me the query to select data from schema_name.table_name without the column column_name. Great!!
The problem: How do I execute the result of the above query?
I tried PREPARE statement, it is just executing the above query and not the result of the above query.
Also, creating a temporary table with no column "column_name" isn't a viable solution.

Answer 1

You need to prepare a dynamic query and then EXECUTE it. It would be something like this:
DO
$do$
BEGIN
EXECUTE (
SELECT CONCAT('CREATE VIEW temp_view AS SELECT ',
-- SELECT table1 columns here
(SELECT STRING_AGG('u1.' || column_name, ', ')
FROM information_schema.columns
WHERE table_name = 'table1'
AND table_schema = 'schema_name'
-- AND column_name NOT IN ('column_name') -- not omitting for table1
),
', ',
-- SELECT table2 columns here
(SELECT STRING_AGG('u2.' || column_name, ', ')
FROM information_schema.columns
WHERE table_name = 'table2'
AND table_schema = 'schema_name'
AND column_name NOT IN ('column_name')),
-- Dynamically prepare the FROM and JOIN clauses
' FROM table1 u1 JOIN table2 u2 ON u1.id = u2.table1_id'));
END
$do$;
CHECK DEMO