Question

我想從不同的表中獲取結果，表格由用戶選擇。所以，我使用表名作爲變量，但它返回nil查詢。

FMResultSet *query = [db1 executeQuery:@"SELECT Image, Explanation FROM %@ WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM %@ WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM %@ WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM %@ WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM %@ WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM %@ WHERE Image !='empty'", [NSString stringWithFormat:@"%@1",tableName], [NSString stringWithFormat:@"%@2",tableName], 
[NSString stringWithFormat:@"%@3",tableName], [NSString stringWithFormat:@"%@4",tableName], [NSString stringWithFormat:@"%@5",tableName], [NSString stringWithFormat:@"%@6",tableName]]; 

如果我對錶名進行硬編碼，它將返回數據。

FMResultSet *query = [db1 executeQuery: 
@"SELECT Image, Explanation FROM Class1 WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM Class2 WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM Class3 WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM Class4 WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM Class5 WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM Class6 WHERE Image !='empty'"]; 

我記錄了tableName值，它返回了正確的值，即「Class」。 請幫我解決這個問題，併爲此提出最佳查詢。

Answer 1

使用此代碼：

FMResultSet *query = [db1 executeQuery:[NSString stringWithFormat:@"SELECT Image, Explanation FROM %@ WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM %@ WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM %@ WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM %@ WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM %@ WHERE Image !='empty'" 
"UNION SELECT Image, Explanation FROM %@ WHERE Image !='empty'", [NSString stringWithFormat:@"%@1",tableName], [NSString stringWithFormat:@"%@2",tableName], 
[NSString stringWithFormat:@"%@3",tableName], [NSString stringWithFormat:@"%@4",tableName], [NSString stringWithFormat:@"%@5",tableName], [NSString stringWithFormat:@"%@6",tableName]]];