2.2

Joining More Than Two Tables

How to Join More than Two Tables

  • To include more tables in the query, you simply add more additional JOIN clauses

Code Snippet:

1    USE world; 
2    SELECT ci.name AS "City Name",
3        co.name AS "Country Name", 
4        cl.language AS "Country Language" 
5    FROM city ci
6        JOIN country co 
7            ON ci.CountryCode = co.Code 
8        JOIN country language cl 
9            ON cl.CountryCode = ci.CountryCode;

Results:

02_joins.png

JOIN countrylanguage cl.

  • The “cl” is the alias for countrylanguage.
  • You can refer to tables already specified in a previous join.

ON cl.CountryCode = ci.CountryCode;

  • The common column between the two tables being joined is the CountryCode column from the countrylanguage table and the CountryCode column from the city table.
  • The “cl” alias previously defined for countrylanguage is used to specify the CountryCode column.