You're right, I meant a failure of the DB/optimiser not the person. Thanks. No they're not perfect but I need them rarely with MSSQL > An optimizer will quick

You're right, I meant a failure of the DB/optimiser not the person. Thanks. No they're not perfect but I need them rarely with MSSQL > An optimizer will quickly run into NP-hard problems like join ordering As a start, dynamic planning based on cardinality estimation based on stats. And then some. It explodes horribly, yes.