Learn in the textbookData Analysis and Preprocessing
DefinitionA data join (データの結合) matches separate tables on the values of a shared column (the key) and combines them into a single table.
ExplanationA join uses a column with the same meaning in both tables, pairs rows whose values match, and places their columns side by side. This yields combinations of information that neither table can show on its own. What happens to rows with no match depends on the type of join; one type, for example, keeps only the rows that matched.
AnalogyIt is like taking your copies of delivery slips, looking up each customer number in the customer register, and writing the recipient's phone number onto each slip.
Memory hookJoin literally means to link up. Picture two tables holding hands through the column they share.