Question

我试图在第二个查询中将一个查询的结果用作WHERE的一部分。我不确定如何最好地解决这个问题，非常感谢任何帮助：

第一次查询：

$result = mysql_query("SELECT `keyword` FROM `history` ORDER BY `last_update` ASC LIMIT 1 ");
while($row = mysql_fetch_array($result))
$keyword = $row['keyword'];

第二次查询

$result = mysql_query("SELECT `id` FROM `data_store` WHERE `keyword`= [result from my first query] ORDER BY `id` DESC LIMIT 1");
while($row = mysql_fetch_array($result))
$id = $row['id'];

为了澄清，keyword.data_store与keyword.history

相关

Answer 1

使用子查询

$result = mysql_query("
SELECT `id` 
FROM   `data_store` 
WHERE  `keyword` = (SELECT `keyword` 
                    FROM   `history` 
                    ORDER  BY `last_update` ASC 
                    LIMIT  1) 
ORDER  BY `id` DESC");
while($row = mysql_fetch_array($result))
$id = $row['id'];

Answer 2

$result = mysql_query("SELECT `id` 
                       FROM `data_store` 
                       WHERE `keyword` = (
                                 SELECT `keyword` 
                                 FROM `history` 
                                 ORDER BY `last_update` ASC 
                                 LIMIT 1 )
                       ORDER BY `id` DESC LIMIT 1");

Answer 3

（剥离PHP方面因为它无关紧要）

SELECT `id` FROM `data_store` WHERE 
  `keyword` IN (
    SELECT `keyword` FROM `history` ORDER BY `last_update` ASC LIMIT 1
  ) 
ORDER BY `id` DESC LIMIT 1

在第二个查询中使用查询结果

3 个答案: