SELECT
a.objid AS acctid,
a.acctno,
a.name,
a.meterid,
m.serialno,
(
SELECT
objid
FROM
waterworks_meter_reading r
WHERE r.meterid = a.meterid
AND r.month = 6
AND r.year = 2015
LIMIT 1
) AS readingid
FROM waterworks_account a
INNER JOIN waterworks_meter m ON a.meterid = m.objid
INNER JOIN waterworks_account_address ad ON a.objid = ad.parentid
WHERE ad.barangayid LIKE '%'
AND readingid IS NULL
當我試圖它上面引發錯誤來執行查詢:在「where子句」未知列「readingid」。有人可以向我解釋爲什麼?未知列在「readingid」「where子句」
是的,它的工作!謝謝! –