Is there a way to join 2 queries of different tables in a single query?

Question

I wonder if there is a way to join 2 queries of different tables in a single query?

For example, in the code below I have 2 queries in separate tables. However, there is a way to perform these 2 queries as a single, at once, instead of having to do 2 variables and two separate queries?

$query1 = mysql_query("SELECT cod_empresa, razao_social FROM tbl_empresa ORDER by razao_social ASC") or die(mysql_error());
$query2 = mysql_query("SELECT cod_tipo, tipo_publicacao FROM tbl_tipo_publicacao by tipo_publicacao ASC") or die(mysql_error());

Answer 1

You can use the instruction UNION, but it needs the number and types of the resulting columns to be equal in both queries.

Ex:

SELECT id, nome FROM alunos
UNION
SELECT id, nome FROM professores

Column names need not be equal.

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The documentation of Mysql explains the use of UNION in detail.