[英]Two mysql queries and 2 $results. Can I get the same 2 $results using only one mysql query?
[英]mysql - querying 2 tables in one query and creating the difference of the two results.
我目前正在PHP中运行两个查询,然后采用每个查询的结果来创建区别:
$sec = 3600;
$sql = "SELECT SUM(REVENUE) as C FROM REVENUE_LOG WHERE ENTRY_DATE BETWEEN (DATE_SUB(NOW(), INTERVAL $secs second)) AND (NOW())";
$res = $this->db->query($sql)->result_array();
$rev = $res[0]['C'];
$sql = "SELECT SUM(COST) as C FROM COST_LOG WHERE ENTRY_DATE BETWEEN (DATE_SUB(NOW(), INTERVAL $secs second)) AND (NOW())";
$res = $this->db->query($sql)->result_array();
$cost = $res[0]['C'];
$profit = $rev - $cost;
是否可以轻松地将其合并为一个查询? 怎么样?
您需要单独运行每个查询,然后将它们作为派生表进行联接:
SELECT R,C, R-C AS difference
FROM (
SELECT SUM(REVENUE) as R
FROM REVENUE_LOG
WHERE ENTRY_DATE BETWEEN (DATE_SUB(NOW(), INTERVAL $secs second)) AND (NOW())
) AS revenue
JOIN (
SELECT SUM(COST) as C
FROM COST_LOG
WHERE ENTRY_DATE BETWEEN (DATE_SUB(NOW(), INTERVAL $secs second)) AND (NOW())
) AS cost;
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