Gilles Collingleft_join in R is silent when keys aren't unique. It just multiplies rows. The output has more rows than the input and nothing tells you.
Julian During@GillesColling If you are using dplyr, you could have a Look at the 'relationship' Parameter. If set, left_join will throw an error.
Cedric R@duringju @GillesColling I was pretty sure there was a warning ? 🤔
But yes, it’s better to always specify the expected relationship.
But yes, it’s better to always specify the expected relationship.