How to check if column exists in the table?

I have two Posts tables like these:

// Posts_1
+----+----------+---------------------------------------------+
| id |   word   |                  mean                       |
+----+----------+---------------------------------------------+
| 1  | hello    | an utterance of “hello”; a greeting.        |
| 2  | what     | asking for information specifying something |
| 3  | light    | provide with light or lighting; illuminate  |
+----+----------+---------------------------------------------+

// Posts_2
+----+----------+---------------------------------------------+-----------+
| id |   word   |                  mean                       |   author  |
+----+----------+---------------------------------------------+-----------+
| 1  | inorite  | I know, right                               | Sajad     |
| 2  | dunno    | I don't know                                | Jack      |
| 3  | lemme    | let me                                      | Ali       |
+----+----------+---------------------------------------------+-----------+

Note: I can't create just one table instead of those two Posts tables. (according to some reasons in reality)

Also I have a Votes table Like this:

// Votes
+----+---------+------------+---------+-----------+
| id | post_id | table_name | user_id | timestamp |
+----+---------+------------+---------+-----------+

And Here is my query to insert a new vote:

INSERT INTO Votes (post_id, table_name, user_id, value, timestamp)
SELECT $post_id, $table_name, $user_id, $value, $timestamp
FROM Dual
WHERE { ? }

Actually I need to a condition which checks if current vote is belong to a such Posts table which has author column , then check this:

... WHERE $author = (SELECT author_id FROM $table_name WHERE id = $post_id)

Note: $table_name is either Posts_1 or Posts_2.

---

Well, Actually I want to give some reputation to author of that post which has achieved a vote. And I need to check $author (if exists) with real author of that post in the database. Is there any solution?