Mysql返回正常但沒有結果

Question

當我嘗試在mysql工作臺中使用子查詢運行select語句時，我遇到沒有結果的OK響應（查詢成功）。我確信代碼是正常的，mysql也沒有發現任何錯誤，但我不知道爲什麼我沒有得到任何答案。

下面的代碼

SELECT date(created_at), 
    (SELECT 
      SUM(amount) AS topup_amount 
     FROM 
      wallet_transaction 
     WHERE 
      type = 'topup' 
     GROUP BY DATE(created_at)), 
    (SELECT 
      SUM(amount) AS admin_add_amount 
     FROM 
      wallet_transaction 
     WHERE 
      type = 'admin_add' 
     GROUP BY DATE(created_at)) 
FROM 
    wallet_transaction; 

Answer 1

看起來你是一個這樣的查詢產生的結果後：

SELECT DATE(wt.created_at)         AS dt_created 
    , IFNULL(SUM(IF(wt.type = 'topup' , wt.amount, 0)),0) AS topup_amount 
    , IFNULL(SUM(IF(wt.type = 'admin_add', wt.amount, 0)),0) AS admin_add_amount 
    FROM wallet_transaction wt 
GROUP BY DATE(wt.created_at) 

---

有幾個與原始查詢的問題。 SELECT列表中的子查詢最多可以返回一行，否則MySQL將引發錯誤。