The hash join is an example of a join algorithm and is used in the implementation of a relational database management system.
The task of a join algorithm is to find, for each distinct value of the join attribute, the set of tuples in each relation which have that value.
Hash joins require an equijoin predicate (a predicate comparing values from one table with values from the other table using the equals operator '=').
Read more about Hash Join: Classic Hash Join, Grace Hash Join, Hybrid Hash Join, Hash Anti-join, Hash Semi-join
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