Как я могу использовать псевдоним MySQL столбец в операторе if

Неизвестный столбец «CURRENT_STOCK_LEVEL» в «списке полей»

$queryString = 'SELECT A.ITEM_CODE, A.BEGINNING_BALANCE AS BEGINNING_BALANCE, B.DELIVERY AS DELIVERY, C.ISSUANCE AS ISSUANCE,
(IFNULL(BEGINNING_BALANCE, 0) + IFNULL(DELIVERY, 0)) - IFNULL(ISSUANCE, 0) AS CURRENT_STOCK_LEVEL , A.REORDERPNT AS REORDERPNT,

IF( CURRENT_STOCK_LEVEL <= REORDERPNT, "LOW", "HIGH") AS STATUS

FROM MM_NEW_ROP_ITEMS AS A
LEFT OUTER JOIN (SELECT ITEM_CODE, SUM(QUANTITY) AS ISSUANCE FROM MM_NEW_ROP_ISSUANCES GROUP BY ITEM_CODE) AS C ON A.ITEM_CODE = C.ITEM_CODE
LEFT OUTER JOIN (SELECT ITEM_CODE, SUM(QUANTITY) AS DELIVERY FROM MM_NEW_ROP_DELIVERIES GROUP BY ITEM_CODE) AS B ON A.ITEM_CODE = B.ITEM_CODE
ORDER BY A.ITEM_CODE';

$query = mysql_query($queryString) or die(mysql_error());

//makes a loop and creates an array with query fields

$items = array();
while($item = mysql_fetch_assoc($query)) {
$items[] = $item;
}

//encodes for JSON format
echo json_encode(array(
"success" => mysql_errno() == 0,
"items" => $items
));

0

Решение

Это ваша SELECT:

SELECT A.ITEM_CODE, A.BEGINNING_BALANCE, B.DELIVERY AS DELIVERY, C.ISSUANCE,
(IFNULL(BEGINNING_BALANCE, 0) + IFNULL(DELIVERY, 0)) - IFNULL(ISSUANCE, 0) AS CURRENT_STOCK_LEVEL ,
A.REORDERPNT AS REORDERPNT,
IF(CURRENT_STOCK_LEVEL <= REORDERPNT, 'LOW', 'HIGH') AS STATUS

Как следует из ошибки, вы не можете повторно использовать псевдоним столбца в том же SELECT утверждение, где оно определено. Это относится не только к SELECT, но также и к другим компонентам запроса, таким как WHERE,

Итак, повторите логику, и я предпочитаю COALESCE() а также CASE (это стандартная функция ANSI):

SELECT A.ITEM_CODE, A.BEGINNING_BALANCE, B.DELIVERY AS DELIVERY, C.ISSUANCE,
(COALESCE(BEGINNING_BALANCE, 0) + COALESCE(DELIVERY, 0)) - COALESCE(ISSUANCE, 0)) AS CURRENT_STOCK_LEVEL ,
A.REORDERPNT AS REORDERPNT,
(CASE WHEN COALESCE(BEGINNING_BALANCE, 0) + COALESCE(DELIVERY, 0)) -
COALESCE(ISSUANCE, 0) <= REORDERPNT
THEN 'LOW' ELSE 'HIGH'
END) AS STATUS
0

Другие решения

Вы можете использовать переменные сеанса MySQL, которые выполняют свою работу, не повторяя логику.

Вот способ сделать это в запросе:

SELECT A.ITEM_CODE, A.BEGINNING_BALANCE AS BEGINNING_BALANCE, B.DELIVERY AS DELIVERY, C.ISSUANCE AS ISSUANCE,
@temp_stock_level:=0, @temp_stock_level:=(IFNULL(BEGINNING_BALANCE, 0) + IFNULL(DELIVERY, 0)) - IFNULL(ISSUANCE, 0) AS CURRENT_STOCK_LEVEL ,
A.REORDERPNT AS REORDERPNT,IF( @temp_stock_level <= REORDERPNT, "LOW", "HIGH") AS STATUS
FROM MM_NEW_ROP_ITEMS AS A
LEFT OUTER JOIN (SELECT ITEM_CODE, SUM(QUANTITY) AS ISSUANCE FROM MM_NEW_ROP_ISSUANCES GROUP BY ITEM_CODE) AS C ON A.ITEM_CODE = C.ITEM_CODE
LEFT OUTER JOIN (SELECT ITEM_CODE, SUM(QUANTITY) AS DELIVERY FROM MM_NEW_ROP_DELIVERIES GROUP BY ITEM_CODE) AS B ON A.ITEM_CODE = B.ITEM_CODE
ORDER BY A.ITEM_CODE;

В этом запросе я использовал переменную @temp_stock_level для хранения значения CURRENT_STOCK_LEVEL

0

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