Join

How it is used

Joins are at the heart of relational databases. The main types are inner join, left (outer) join, right join, full outer join and cross join. People 'join A to B' or 'join A with B on customer_id', and complain about queries with 'too many joins'.

Example sentences

1. Join the orders table to customers on customer_id to get the customer names.

2. The report is slow because of a join on a column without an index.

Common collocations

• join two tables
• join on a column
• self-join
• join condition
• cross join

Related terms

• inner joinA join that returns only the rows that have a match in both tables; rows without a partner on the other side are left out.
• left joinA join that returns all rows from the first (left) table and the matching rows from the second; where there is no match, the second table's columns are NULL.
• foreign keyA column in one table that points to the primary key of another table, linking the two and stopping you from storing references to rows that do not exist.
• SELECT statementThe SQL statement that reads data from one or more tables and returns the matching rows without changing anything in the database.

This word in other fields

The same English word can have a different meaning in another field:

• join · Data Science & Analytics
• join · Databases & SQL

More terms: Databases and Persistence

• SQL
• table
• column
• query
• relational database
• DBMS
• primary key
• WHERE clause
• schema
• transaction
• data type
• NULL