[英]How to perform two select statements simultaneously on two tables in MySQL using PHP
什么是運行此查詢的最佳方法。
我在同一個數據庫中有兩個表,products和shop_orders。 我正在嘗試運行兩個select語句,使用shop_orders中的字段之一來檢索數據。
<td align="center" bgcolor="#F5F5F5" class="column-light"><strong>Chain Men's Shoes</strong></td>
<td align="center" bgcolor="#F5F5F5" class="column-light"><strong>
<?
$sql="
SELECT * FROM shop_orders WHERE
DATE(CONCAT(shop_order_year,'-',shop_order_month,'-',shop_order_day))
BETWEEN '".$start."' and '".$end."'
AND shop_order_action = 'Sale' AND shop_order_field_to_update NOT LIKE '%con%' AND shop_order_location = 'Chain' ORDER BY shop_order_id DESC";
$result=mysql_query($sql);
while($rows=mysql_fetch_array($result)){ ?>
<? $shop_order_product_id = $rows['shop_order_product_id'];?>
<?
$sql2="SELECT * FROM product WHERE product_id='".$rows['shop_order_id']."' AND category = 'Mens'";
$result2=mysql_query($sql2);
$mens_shoes=mysql_num_rows($result2);
echo $mens_shoes; ?>
</strong></td> <?
}
?>
DB Structure
Product
Product ID Category
1234 Mens
2345 Mens
Shop_orders
shop_order_day shop_order_month shop_order_year shop_order_action
1 03 2014 Sale
shop_order_product id shop_order_field_to_update
1234 quantity_c_size_39
相似的字段是shop_order_product_id和產品ID。
此查詢應在給定日期段內總計銷售數量,其中匹配條件為地理位置,action = Sale,類別為Mens。 該查詢的第一部分($ sql)已經有效,但是,當我嘗試將其與第二個嵌入式SELECT語句結合使用時,返回的數字為零。 我知道這個數字應該大於零。
有什么幫助嗎?
*更新*
我似乎用這個解決了這個問題:
$sql="
SELECT COUNT(*) FROM shop_orders
LEFT JOIN product
ON shop_orders.shop_order_product_id=product.product_id
WHERE
DATE(CONCAT(shop_order_year,'-',shop_order_month,'-',shop_order_day))
BETWEEN '".$start."' and '".$end."'
AND category = 'Mens' AND shop_order_action = 'Sale' AND shop_order_field_to_update NOT LIKE '%con%' AND shop_order_location = 'Chain' GROUP BY shop_order_id";
我建議您學習更多sql。
該語句將幫助您:
http://www.w3schools.com/sql/sql_join.asp
使用此語句,您可以執行以下操作:
SELECT * FROM t1 JOIN t2 on t1.id WHERE ........;
您可能還需要此:
如果您的表是通過前瞻性鍵鏈接的,則可以將它們聯接起來,並使用單個sql quethem對所有值進行計數,方法是:
$sql="SELECT * FROM shop_orders
LEFT JOIN product ON product.product_id=shop_order_product_id
WHERE
DATE(CONCAT(shop_order_year,'-',shop_order_month,'-',shop_order_day)) BETWEEN '".$start."' and '".$end."'
AND shop_order_action = 'Sale' AND shop_order_field_to_update NOT LIKE '%con%' AND shop_order_location = 'Chain' ORDER BY shop_order_id DESC
";
左連接子句ON應該是shop_orders前鍵與生產主鍵之間的鏈接(如果數據庫中具有1到許多數據邏輯結構)
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