SQL Joins Explained: Inner, Left, Right, and Full Join Differences

SQL joins combine rows from two tables based on a shared column, typically an ID, but each join type handles unmatched rows differently. An inner join returns only rows with matches on both sides, discarding any unmatched records from either table. A left join retains all rows from the left table, filling in NULLs where no match exists in the right table, while a right join does the opposite. A full join preserves all rows from both tables, using NULLs to fill gaps wherever a match is absent. Developers are advised to use an inner join by default and switch to other types only when unmatched rows are relevant to the query.