Overwrite some inherited methods on PostgresTable

Some postgres columns (e.g. if they have a capital letter) need to be
surrounded by double quotes

parsons/databases/postgres/postgres.py

@@ -3,6 +3,7 @@
 from parsons.databases.alchemy import Alchemy
 from parsons.databases.database_connector import DatabaseConnector
 from parsons.etl.table import Table
+from typing import Optional
 import logging
 import os
 
@@ -102,4 +103,35 @@ def table(self, table_name):
 class PostgresTable(BaseTable):
     # Postgres table object.
 
-    pass
+    def max_value(self, column: str):
+        """Get the max value of this column from the table."""
+        return self.db.query(
+            f"""
+            SELECT "{column}"
+            FROM {self.table}
+            ORDER BY "{column}" DESC
+            LIMIT 1
+            """
+        ).first
+
+    def get_updated_rows(
+        self,
+        updated_at_column: str,
+        cutoff_value,
+        offset: int = 0,
+        chunk_size: Optional[int] = None,
+    ) -> Table:
+        """Get rows that have a greater updated_at_column value than the one provided."""
+        sql = f"""
+            SELECT *
+            FROM {self.table}
+            WHERE "{updated_at_column}" > %s
+        """
+        if chunk_size:
+            sql += f" LIMIT {chunk_size}"
+
+        sql += f" OFFSET {offset}"
+
+        result = self.db.query(sql, parameters=[cutoff_value])
+
+        return result