MySQL查詢與多個AND條件

Question

我不知道為什么我的SQL查詢不起作用

TABLE用戶

userid   firstname    lastname
1         JOHN         DEO
2         JANE         DEO

表味精

msg_id  msg_from   msg_to     received  age  city  country    product  weight  price     timestamp            
1       userid(1)  userid(2)  null      26   any   any         rice     25     $100      2018-10-04 14:37:12

我的查詢：

SELECT SND.userid, SND.firstname, SND.lastname, M.age, M.city, M.country
FROM msg as M
JOIN users as SND 
ON SND.userid = M.msg_from
WHERE M.msg_to = 'userid 1' AND product = 'rice' AND price >='$100'

我看不到任何問題，但無法獲得結果

Answer 1

假設userid / msg_to / msg_from是整數，而msg表中的price是一個數字，我將WHERE子句更改為

WHERE M.msg_to = 1 AND product = 'rice' AND price >= 100.0

如果它們是字符串，那么您可以做

WHERE M.msg_to = '1' AND product = 'rice' AND CAST(price AS DECIMAL(10,2)) >= 100.0

假設您放下美元符號。

Answer 2

如果您想獲得結果，請執行以下查詢

SELECT SND.userid, SND.firstname, SND.lastname, M.age, M.city, M.country
FROM msg as M
JOIN users as SND 
ON SND.userid = M.msg_from
WHERE M.msg_to = 'userid 2' AND product = 'rice' AND price >='$100'

在您的代碼結果中未顯示，因為根據您的表視圖，userid與msg_to列不匹配