I had difficulty explaining the purpose and organisation of databases with Y3 children until I realised that a perfect child friendly data base comes in the form of Top Trumps games. 

I give each child a card to locate information from, they then compare their information in groups and choose the card that they think has the best chance of winning in a game of Top Trumps - this gives them the opportunity to locate and compare data and make choices. 

They then play a brief game as a class using only the one card from each group. 

They then come up with ideas for making their own game and deciding which facts they should include on each card.