php - mysql 选择变量设置位置

Question

我有两个表:

• 销售
• sales_size

我想查询受变量 $gender、$category 和 $brand 约束的 sales_sizes。

如果设置了各个变量，如何执行 where 语句，如果未设置，则如何不将它们包含在查询中？

[括号内为伪代码]

SELECT size, country
FROM `sales_sizes` WHERE sale_id IN (
    SELECT sale_id
    FROM `sales`
    WHERE [gender = $gender if $gender isset]
    AND [category = $category if $category isset]
    AND [brand = $brand if $brand isset]

) 

Answer 1

您可以将变量收集到数组中，然后像这样处理它:

$gender   = 'f';
$category = null;
$brand    = 'foo';

$rgCondition = ['gender'=>$gender, 'category'=>$category, 'brand'=>$brand];
$rgCondition = array_filter($rgCondition, function($x)
{
   //strip null-ed values:
   return isset($x);
});
$rgWhere     = [];

foreach($rgCondition as $sField=>$mValue)
{
   $rgWhere[] = '`'.$sField.'` = "'.$mValue.'"';   
}
$sWhere = count($rgWhere)?' WHERE '.join(' && ', $rgWhere):'';
//var_dump($sWhere);

-我已经跳过了字符串转义，但不要忘记它。