Php / MySql 从不同的表中找到重复的记录，并参考它们来自哪里

Question

I've 2 tables, "amigos" and "socios". In amigos I've rows id, nr_amigo, nome In socios I've rows id, nr_socio, nome

I need to search in both tables if there are duplicated records

If I use

SELECT id, nr_amigo as amigo FROM amigos WHERE nome = :variavel
UNION
SELECT id, nr_socio as socio FROM socios WHERE nome = :variavel

It works, BUT I can't know from wich table the found match has come

So my question is how do I list duplicated records (if any) and How do I know where did they came from?

In php I've

$sql_pesquisar -> execute($dados_a_enviar);
$num_rows_query = $sql_pesquisar -> rowCount();
if ($num_rows_query > 0) {
    while($row = $sql_pesquisar -> fetch(PDO::FETCH_ASSOC)) {
        print_r($row);
    }
}

Result is

Array
(
    [id] => 180
    [nr_amigo] => 180
)

But in fact that record is from "socios" and not from "amigos"

Thanks!

Answer 1

You can add a new column as tablename in the select list to identify the table. Final query will be like

SELECT id, 'amigos' as tablename, nr_amigo as amigo FROM amigos WHERE nome = :variavel
UNION
SELECT id, 'socios' as tablename, nr_socio as socio FROM socios WHERE nome = :variavel

You can then identify using tablename column in php to determine which table the record belongs to.

Answer 2

There is another option besides the one @ascsoftw mentioned in his answer.

You can select null to the column you are not selecting in current subquery like this

SELECT id, nr_amigo AS amigo, NULL as socio FROM amigos WHERE nome = :variavel
UNION ALL
SELECT id, NULL AS amigo, nr_socio AS socio FROM socios WHERE nome = :variavel

The result will then look like

Array
(
    [id] => 180
    [amigo] => 180
    [socio] => null
)

or

Array
(
    [id] => 180
    [amigo] => null
    [socio] => 180
)

Make sure to use UNION ALL if you want to list duplicate entries.