Mysql比较2个表

Question

如何比较不同表中的三个值？

    pm_meta
    +----+----------+--------+----------+
    | id | item_id  |meta_key|meta_value|
    +----+----------+--------+----------+
    |  2 |     100  | google |googl.com |
    |  3 |     101  | yahoo  |yahoo.com |
    |  3 |     102  | msn    |msn.com   |
    +----+----------+--------+----------+

    pm_embed_code
    +------+-----------+------------+
    | id   | uniq_id   |embed_code  |
    +------+-----------+------------+
    |  100 |     abcd  |<iframe src=|
    |  101 |     dddc  |<iframe src=|
    |  102 |     ffdd  |<iframe src=|
    +----+----------+------------+



    $sql = "SELECT * 
            FROM pm_embed_code, pm_meta
            WHERE pm_embed_code.uniq_id = 'abcd'
            AND pm_embed_code.id = pm_meta.item_id
            AND pm_meta.meta_key = 'google' ";

    echo $row['meta_value']; // I want result "googl.com"

我想检查 pm_embed_code.uniq_id= abcd 并选择 pm_embed_code.id，然后检查 pm_embed_code.id = pm_meta.item_id 和另外，如果pm_meta.meta_key = google并且如果全部打印meta_value

更新:

 $sql = "SELECT * 
            FROM pm_meta
            WHERE pm_meta.meta_key = 'google' ";

echo $row['meta_value'];

这个也没有显示任何...为什么？

Answer 1

查询:

选择 pmc.id 作为“pm_embed_code.id”，pm.meta_key AS“pm_meta.meta_key” FROM pm_meta pm LEFT OUTER JOIN pm_embed_code pmc ON pmc.id = pm.item_id WHERE pmc.uniq_id = “abcd” AND pm。 meta_key = '谷歌'

代码

$sql = "SELECT pmc.id as "pm_embed_code.id", pm.meta_key AS "pm_meta.meta_key"FROM pm_meta pm LEFT OUTER JOIN pm_embed_code pmc ON pmc.id = pm.item_id WHERE pmc.uniq_id = "abcd “并且 pm.meta_key = 'google';”

回显$row["pm_meta.meta_key"];