The ERC721 Marketplace Subgraph
This Subgraph acts as a market aggregator for 3 marketplaces (all sale events from OpenSea, LooksRare, and X2Y2) and indexes all ERC721 NFT transfer activity.
This guide explains the ERC721 Marketplace Subgraph and how to interact with it.
Github Repo - source code for deployed Subgraph.
You can utilize this Subgraph to get any sales realted info happened on OpenSea, LooksRare, and X2Y2. You can also query any info regarding any ERC721 NFT collection. All of which will be explained in details in the next section.
To learn more about querying a subgraph refer to The Graph's documentation.