Join may refer to:

• Join (law), to include additional counts or additional defendants on an indictment
• In mathematics:
  • Join (mathematics), a least upper bound of set orders in lattice theory
  • Join (topology), an operation combining two topological spaces
  • Join (relational algebra), a type of binary operator
• Join (SQL), a SQL and relational database operation
• join (Unix), a Unix command
• Join-calculus, a process calculus developed at INRIA for the design of distributed programming languages
• Joins (concurrency library), a concurrent computing API from Microsoft Research
• Join Network Studio of NENU, a non-profit organization of Northeast Normal University
• Joins.com, the website for South Korean newspaper JoongAng Ilbo

A SQL join clause combines records from two or more tables in a database. It creates a set that can be saved as a table or used as is. A JOIN is a means for combining fields from two tables by using values common to each. ANSI standard SQL specifies four types of JOIN: INNER, OUTER, LEFT, and RIGHT. As a special case, a table (base table, view, or joined table) can JOIN to itself in a self-join.

Join (engl. ‚Verbindung, verbinden‘) steht für