He was asking about inner join, left join, right join, and full outer join. What will be the output of table A and table B?

In SQL, a join combines rows from two tables based on a related column.

• Inner Join: Returns only rows where the join condition is true in both tables. If table A has ids 1,2,3 and table B has ids 2,3,4, the inner join on id will return rows for ids 2 and 3.

• Left (Outer) Join: Returns all rows from the left table (A) and matching rows from the right table (B). Rows in A that have no match in B will have NULLs for B’s columns. Using the same example, the left join would return rows for ids 1,2,3; id 1 would have NULL for B.

• Right (Outer) Join: Symmetric to left join, but returns all rows from the right table (B). In the example, rows for ids 2,3,4 would be returned; id 4 would have NULL for A.

• Full Outer Join: Returns all rows when there is a match in either table. It combines the results of left and right joins. In the example, ids 1,2,3,4 would all appear; ids 1 and 4 would have NULLs on the side that lacks a match.

These results illustrate how each join type affects the row count and which rows are included.