Fix duplicate fetch (#26)

* fix wrong max block number return

* add README announcement

README.rst

@@ -18,6 +18,13 @@ This library is a local tracker of transactions for the Ethereum chain and the B
 It is a simple interface with the `etherscan <https://etherscan.io>`_ and the
 `bscscan <https://bscscan.com>`_ APIs and will save locally the results to gain time and avoid over-calling the APIs.
 
+Announcement
+-------
+
+If you previously used this library with a version inferior to 0.1.3,
+please head `here <https://github.com/EtWnn/ScanWatch/discussions/25>`_ to correct a potential bug in the database.
+
+
 Quick Tour
 ----------
 

ScanWatch/storage/ScanDataBase.py

@@ -78,16 +78,13 @@ def get_last_block_number(self, address: str, nt_type: NETWORK, net: str, tr_typ
         :rtype: int
         """
         table = get_transaction_table(address, nt_type, net, tr_type)
-        selection = f"MAX({table.blockNumber})"
-        result = self.get_conditions_rows(table, selection=selection)
+        selection = str(table.blockNumber)
+        query = self.get_conditions_rows(table, selection=selection)
         default = 0
         try:
-            result = result[0][0]
-        except IndexError:
+            return max([int(e[0]) for e in query])
+        except ValueError:
             return default
-        if result is None:
-            return default
-        return int(result)