Difference between Join and Concatenate

Join means that the columns in both tables are compared and the join is made over those columns that have the same column names.

This means that if multiple columns are shared between tables, the match will be made over the distinct combinations of those columns

*By default, Qlikview performs an outer join

Let’s have clear picture of the join 

Concatenate

Concatenate just appends the rows of one table to another. Concatenate never merges any rows. The number of rows in a concatenated table is always the sum of the rows from the two input tables. Here's what our sample data will look like after Concatenate.

Difference

Instead of matching and merging rows between tables, this statement appends the rows of one table to another

Let’s have clear picture of the Concatenate