是否存在一个函数，对于dataSet_1中的每个值，在基于多个条件的dataSet_2中进行搜索？ 就像在SQL中一样，对于每个值，都要进行新的搜索。
SELECT
value1Table1,
value2Table1,
(
SELECT MIN(value) FROM table_2 AS table_2
WHERE table_2.value1 = table_2.value1 AND table_1.Date > table_2.Date
) AS value1table2,
value3Table1
FROM table_1
从MAX更改为MIN并且＆lt;对于＆gt;查询以下示例：
我会尝试解释一下。通常情况下，在我有日期（factDate）和每个用户（具有您自己的不同日期）的情况下，我会使用类似的东西。我需要搜索在factDate之后发生的第一个事件。
示例：
TABLE_1
|User|TargetEventDate|NextEventDate| <- Value that I want
|A |2018-04-17 |2018-04-18 | <- Value to Find
|B |2018-04-14 |2018-04-15 | <- Value to Find
TABLE_2
|User|DateEvent |
|A |2018-04-19|
|A |2018-04-18| <- Value that I want for user A
|A |2018-04-17| <- Value used in Table_1 for user A
|A |2018-04-13|
|A |2018-03-10|
|B |2018-04-17|
|B |2018-04-15| <- Value that I want for user B
|B |2018-04-14| <- Value user in Table_1 for user B
答案 0 :(得分：1)
由于相关子查询中的add_filter( 'woocommerce_add_to_cart_validation', 'limit_cart_items_from_category', 10, 3 );
function limit_cart_items_from_category ( $passed, $product_id, $quantity ){
// HERE define your product ID
$targeted_product_id = 37;
// Check quantity and display notice
if( $quantity > 1 && $targeted_product_id == $product_id ){
wc_add_notice( __('Only one item quantity allowed for this product', 'woocommerce' ), 'error' );
return false;
}
// Loop through cart items checking if the product is already in cart
foreach ( WC()->cart->get_cart() as $cart_item ){
if( $targeted_product_id == $product_id && $cart_item['data']->get_id() == $targeted_product_id ) {
wc_add_notice( __('This product is already in cart (only one item is allowed).', 'woocommerce' ), 'error' );
return false;
}
}
return $passed;
}
// Checking and removing quantity field for a specific product
add_filter( 'woocommerce_quantity_input_args', 'custom_quantity_input_args', 10, 2 );
function custom_quantity_input_args( $args, $product ) {
// HERE define your product ID
$targeted_product_id = 37;
if( $targeted_product_id == $product->get_id() )
$args['min_value'] = $args['max_value'] = $args['input_value'] = 1;
return $args;
}
子句，我没有看到将查询重写为更简单的方法的方法。但是，好消息是R有一个名为WHERE的包，它实际上可以执行常规的SQL查询。
sqldf我在此假设library(sqldf)
query <- "SELECT t1.value1Table1, t1.value2Table1,
(SELECT MAX(value) FROM table_2 t2
WHERE t1.value1 = t2.value1 AND t1.Date < t2.Date) AS value1table2,
t1.value3Table1
FROM table_1"
result <- sqldf(query)
和table_1是实际数据框，其中的列对应于查询所引用的列。