PHP的MySQL如果總和不工作

Question

trans_id  trans_product  trans_user  trans_date  trans_date2  trans_description  trans_inventory
     13         6              1     1278604284   1278547200                     -1000
      9         5              1     1278601462   1278547200    New Arrival        200
     11         7              1     1278601743   1278547200                        50
     12         6              1     1278601756   1278547200                      5000

$sql = mysql_query("SELECT *, SUM(IF(trans_inventory>0,trans_inventory,0)) as pos "
                  +"FROM site_trans GROUP BY trans_product") or die(mysql_error());
while($row = mysql_fetch_array($sql)) {
    $amt_p = $row['pos'];
    $sql2 = mysql_query("SELECT *, SUM(IF(trans_inventory<0,trans_inventory,0)) as neg "
                      + "FROM site_trans GROUP BY trans_product") or die(mysql_error());
    while($row2 = mysql_fetch_array($sql2)) {
        $amt_n = $row2['neg'];
    }

    echo $amt_p; //working
    echo $amt_n; // not working
}

第一個sql查詢正在工作（$ amt_p），但是第二個sql查詢是否為負不工作（$ amt_n）任何想法我做錯了什么？

Answer 1

您將為每個產品覆蓋$amt_n 。 我建議將查詢合並成這樣：

$sql = mysql_query("SELECT *, "
                  + "SUM(IF(trans_inventory>0,trans_inventory,0)) as pos, "
                  + "SUM(IF(trans_inventory<0,trans_inventory,0)) as neg "
                  + "FROM site_trans GROUP BY trans_product") or die(mysql_error());
while($row = mysql_fetch_array($sql)) {
    $amt_p = $row['pos'];
    $amt_n = $row['neg'];

    echo $amt_p;
    echo $amt_n;
}

Answer 2

加$amt_n = 0進行初始化
更改$amt_n = $row2['neg']; 到$amt_n += $row2['neg'];

問題是您在對其進行迭代時將值歸零

您需要對pos和neg都這樣做

直流電

Answer 3

不知道為什么它不起作用，但是在我看來，您只需要所有正負trans_inventory行。 您如何在第一個查詢中添加“ where trans_inventory> 0”，並擺脫條件IF條件呢？

SELECT *, SUM(trans_inventory) as pos 
FROM site_trans
WHERE trans_inventory>0
GROUP BY trans_product

您所說的“不工作”到底是什么意思？ 您獲得什么價值，您期望什么？