将列名列表传递给 psycopg2 中的查询

Question

I have the following query:

select distinct * from my_table where %s is NULL;

I would like to be able to pass in more than one column name to this query, but I do not know how many columns I will want to be checking for nulls every time.

How can I use query parameter techniques like the above to make both the below queries from the same statement?:

select distinct * from my_table where "col1" is NULL or "col2" is NULL;
select distinct * from my_table where "col1" is NULL or "col2" is NULL or "col3" is NULL;

I would appreciate an answer that includes being able to get the below as well, but it is not necessary in this case:

select distinct * from my_table where "col1" is NULL;

(I am using Amazon Redshift, in case that removes an postgresql-related possibilities)

Answer 1

query = '''
    select distinct *
    from my_table
    where
        %s or
        "col1" is NULL and %s or
        "col2" is NULL and %s or
        "col3" is NULL and %s
'''

Pass True to the conditions which you want to be evaluated. Say you want rows where any of col1 and col2 are null :

cursor.execute(query, (False, True, True, False))

If you want all rows regardless:

cursor.execute(query, (True, False, False, False))

BTW double quoting identifiers is a bad idea.