如何从两个表中获取值？

Question

I have two tables A and B , table A contains some columns and table B have some columns , there is one column same in both tables.

I have a value for table B and and based on that value i have to find another column' rows value , and based on those values(which got from table B ) ,i have to find some columns rows from table A

Answer 1

You will need to use the INNER JOIN statement :

Example of tables :

Table A : A.id, A.column1, A.column2 Table B : B.id, B.column1, B.column2, B.a_id

SQL

SELECT * FROM A INNER JOIN B ON B.a_id = A.id

PHP

$dbh = new PDO('mysql:host=localhost;dbname=test', $user, $pass);
$sql = 'SELECT * FROM A INNER JOIN B ON B.a_id = A.id';
foreach ($dbh->query($sql) as $row) {
   var_dump($row);
}

Answer 2

A simple join query:

SELECT a.*,b.*
FROM B
INNER JOIN A
 ON(A.<Same_Col> = B.<Same_Col>)

Switch a.*,b.* to the columns you want to select.

You can read about joins syntax here.