British Sign Language Glossaries of Curriculum Terms

BSL Data Science Glossary - Join - left definition

Definition: Left join is where we add columns from the second table to the first table. For example, with the first table, let's say there's a row about myself, called Ben, with my age in another column. The second table has exam results, so it has exam results as well as names. If we want to do a left join, we check the first table, looking at each row, looking at the name, let's say the name is Ben. We check the second table, if it has a row about Ben, then we add Ben's exam results to the first table to the same row with his age. Next person on the first table is Pip and we see that there isn't a Pip in the second table. In this case, we keep Pip in the first table albeit without his exam results. So, we're only adding columns from the second table, while keeping all rows on the first table.