Joins: Retrieving Data from Several Tables

A join operation compares two or more tables (or views) by specifying a column from each, comparing the values in those columns row by row, and linking the rows that have matching values. It then displays the results in a new table. The tables specified in the join can be in the same database or in different databases.

You can state many joins as subqueries, which also involve two or more tables. See Chapter 5, "Subqueries: Using Queries Within Other Queries."

When Component Integration Services is enabled, you can perform joins across remote servers. For more information, see the Component Integration Services User's Guide.

How joins work

Join syntax

Joins and the relational model

How joins are structured

The from clause

The where clause

How joins are processed

Equijoins and natural joins

Joins with additional conditions

Joins not based on equality

Self-joins and correlation names

The not-equal join

Not-equal joins and subqueries

Joining more than two tables

Outer joins

Inner and outer tables

Outer join restrictions

Views used with outer joins

ANSI Inner and outer joins

ANSI outer joins

Transact-SQL outer joins

How null values affect joins

Determining which table columns to join


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