Источник: sql-join.com


INNER JOIN

Select all records from Table A and Table B, where the join condition is met.

LEFT (Outer) JOIN

Select all records from Table A, along with records from Table B for which the join condition is met (if at all).

RIGHT JOIN

Select all records from Table B, along with records from Table A for which the join condition is met (if at all).

FULL JOIN

Select all records from Table A and Table B, regardless of whether the join condition is met or not.

Example

Let’s use the tables we introduced in the “What is a SQL join?” section to show examples of these joins in action. The relationship between the two tables is specified by the customer_id key, which is the “primary key” in customers table and a “foreign key” in the orders table:

Table 1

customer_id first_name last_name email address city state zipcode
1 George Washington [email protected] 3200 Mt Vernon Hwy Mount Vernon VA 22121
2 John Adams [email protected] 1250 Hancock St Quincy MA 2169
3 Thomas Jefferson [email protected] 931 Thomas Jefferson Pkwy Charlottesville VA 22902
4 James Madison [email protected] 11350 Constitution Hwy Orange VA 22960
5 James Monroe [email protected] 2050 James Monroe Parkway Charlottesville VA 22902

Table 2

order_id order_date amount customer_id
1 July 4, 1776 234.56 1
2 March 14, 1760 78.5 3
3 May 23, 1784 124 2
4 September 3, 1790 65.5 3
5 July 21, 1795 25.5 10
6 November 27, 1787 14.4 9