在mysql中联接两个表并从第二个表中读取值

Question

I want to display the names by matching the value of att_card_no in the ent table to cardno in the att_user table.

try {
    $att = $att->query('select att_time,att_date,att_card_no from att_detail WHERE att_card_no IN (select name from att_user where cardno="2342323423")');
    $att -> execute();
    $result = $att -> fetch();
}
catch (PDOException $e){
    echo $att . "<BR>" . $e->getMessage();
}

    $att -> execute();
?>


    <?php echo "Name: ".$result['att_card_no']; ?>



Table:att_detail
+---------+----------+-------------+------------+
| no      | att_time | att_date    | att_card_no|
+---------+----------+-------------+------------+
|       1 | 08:01    | 11-12-17    | 2342323423 |
|       2 | 08:02    | 12-12-17    | 4574574577 |
|       3 | 08:03    | 13-12-17    | 4656456796 |
|       4 | 08:04    | 14-12-17    | 9343450984 |
+---------+----------+-------------+------------+

Table: att_user
+----+-------------+-------------+
| no |    name     |    cardno   |
+----+-------------+-------------+
|  1 | name1       |  2342323423 |
|  2 | name2       |  4574574577 |
|  3 | name3       |  4656456796 |
|  4 | name4       |  9343450984 |
+----+-------------+-------------+

But the name value from att_user is not displayed. Appreciate in understanding what is wrong here. There are no errors throwing up too.

Edit: If you cannot answer it or if you find a similar Q that solves my problem please let me know because my searches did not find any but down voting this question is not helping a bit

Answer 1

There are several problems with your SQL statement.

Since name isn't in the select's list of columns, it won't be in the result set. In your where, you are trying to match on att_card_no = name which won't ever match.

Here's your SQL statement:

select 
    att_time,
    att_date,
    att_card_no 
from att_detail 
WHERE att_card_no IN (select name from att_user where cardno="2342323423")

But this is what you really want:

select 
    b.`name`,
    a.`att_time`,
    a.`att_date`,
    a.`att_card_no` 
from ent a 
JOIN att_user b
ON a.`att_card_no` = b.`cardno`;

Answer 2

You need to use JOIN query like below:-

(SELECT att_user.name,att_detail.att_time,att_detail.att_date,att_detail.att_card_no FROM att_user LEFT JOIN att_detail on  att_user.cardno = att_detail.att_card_no WHERE att_user.cardno="2342323423");

Note:-

You query is actually converted like this:-

'select att_time,att_date,att_card_no from att_detail WHERE att_card_no IN ("name1")'

So basically no name column is selected there, and hens it not coming.

Answer 3

you should use a JOIN

 $att = $att->query('
    select a.att_time
    , a.att_date
    , a.att_card_no 
    , b.name 
  from att_detail  as a
  inner join att_user as b on a.att_card_no = b.card_no and b.cardno="2342323423"'