互動式查詢

Question

有沒有一種方法來創造一個爲用戶提供一個對話框提示輸入值X來完成以下查詢的查詢：

SELECT X AS DISTANCE, 
SUM(ABS(LOCX) <= X AND ABS(LOCY) <= X) AS QUANTITY, 
COUNT(*) AS TOTAL, 
CONCAT(AVG(ABS(LOCX) <= X AND ABS(LOCY) <= X)*100, '%') AS PERCENTAGE 
FROM CUSTOMER; 

Answer 1

假設你編碼的應用程序，其中用戶提供輸入，有多種方法來創建使用這些值作爲變量的查詢 - 一個方法如下：

SET @t1=1, @t2=2, @t3:=4; 
SELECT @t1, @t2; 

來源：http://dev.mysql.com/doc/refman/5.5/en/user-variables.html

所以爲您的特定情況下，MySQL的語法替換的X所有的情況下，用戶定義的變量@X，它會是這個樣子：

SET @X = user_input; 
SELECT @X AS DISTANCE, 
SUM(ABS(LOCX) <= @X AND ABS(LOCY) <= @X) AS QUANTITY, 
COUNT(*) AS TOTAL, 
CONCAT(AVG(ABS(LOCX) <= @X AND ABS(LOCY) <= @X)*100, '%') AS PERCENTAGE 
FROM CUSTOMER;