How to build a database on Algorand?

if you want your data on-chain, then it should be either in the application global/local state. or NOTE field of the transaction(which is not preferred).
Another way could be to have this data on decentralized storage services like IPFS/file coin etc and save the hash in the asset URL.

Why do I get the error: should have been authorized by XXX but was actually authorized by XXX

txn1 should be signed by the private key of address-1
txn2 should be signed by the private key of address -2
if you get this error even after doing the same, then one of the accounts was rekey-ed to a different account.

AssetParam not working pyteal

assetClawbackExpr = AssetParam.clawback(Int(0))
assetClawbackAddr = Seq([
    assetClawbackExpr,
    assetClawbackExpr.value()
])
Assert(assetClawbackAddr == verifiedaddr)