Add compiler version issues

Author: kuzdogan

docs/2. database-schema.md

@@ -28,3 +28,16 @@ Therefore, the bytecode string from the DB **will not be identical** to the outp
 :::
 
 <iframe src='https://dbdiagram.io/e/66575805b65d93387902b460/6657580cb65d93387902b52e' style={{width: "100%", height: "500px"}}> </iframe>
+
+## Notes on the data
+
+We will be documenting the known inconsistencies in the data below:
+
+- **Compiler versions**
+  - Blockscout writes versions with a `v` prefix: `v0.3.0` but Sourcify and Routescan do not `0.3.0`
+  - **Vyper:** Keep in mind the vyper version build strings are not consistent (details [here](hhttps://github.com/ethereum/sourcify/issues/2247#issuecomment-3155878775)):
+    - version =< 0.3.0: The commit hash has 7 characters `0.3.0+commit.8a23feb`
+    - version 0.3.1: No commit hash: `0.3.1`
+    - version >= 0.3.2: The commit hash has 8 characters `0.3.2+commit.3b6a4117`
+
+See discussed changes for the next v2 schema [here](https://github.com/verifier-alliance/database-specs/issues/30).