在FMDatabase爲iOS

Question

使用像「東西％％」我不知道這是不是真的，但我被告知，FMDatabase執行更好，如果你這樣做

NSString *query = [NSString stringWithFormat:@"SELECT * FROM db where col=?"]; 
FMResultSet *rs = [theDatabase executeQuery:query, columnToLookFor]; 

vs 

NSString *query = [NSString stringWithFormat:@"SELECT * FROM db where col='columnToLookFor'"]; 
FMResultSet *rs = [theDataBase executeQuery:query]; 

因此，我們有一個搜索查詢，這是否：

NSString *query = [NSString stringWithFormat:@"SELECT Symbol, Category FROM Symbols where Category like \"%%%@%%\" or Symbol like \"%%%@%%\" group by Symbol, Category order by Category", searchtext, searchtext]; 
FMResultSet *rs = [theDatabase executeQuery:query]; 

我想這個更改爲：？然而，在第二形式與

NSString *query = [NSString stringWithFormat:@"SELECT Symbol, Category FROM Symbols where Category like \"%%?%%\" or Symbol like \"%%?%%\" group by Symbol, Category order by Category"]; 
FMResultSet *rs = [theDatabase executeQuery:query, searchtext, searchtext]; 

，我FMResultSet是0，我ñ確信我在這種情況下做錯了什麼。這會加速我們的搜索嗎？或者更糟糕的是，這個功能需要花費很長時間才能實現。

Answer 1

應該沒有理由爲什麼一個人會工作，而另一個人不會工作，假設你的第一個searchtext變量是一個問號，因爲你正在將第二個字符串放入SQL字符串中。你可能想改變兩行這樣的：

NSString *query = [NSString stringWithString:@"SELECT Symbol, Category FROM Symbols where Category like '%%?%%' or Symbol like '%%?%%' group by Symbol, Category order by Category"]; 
FMResultSet *rs = [theDatabase executeQuery:query]; 

此外，行前我就這樣做只是爲了看看有什麼SQL正在尋找時，它正被FMDB處理，如：

[theDatabase setTraceExecution:YES]; 

編輯：請嘗試更改到此，看到了跟蹤執行這樣說：

NSString *query = [NSString stringWithString:@"SELECT Symbol, Category FROM Symbols where Category like '%%?%%' or Symbol like '%%?%%' group by Symbol, Category order by Category"]; 
FMResultSet *rs = [theDatabase executeQuery:query, searchtext, searchtext, nil]; 

Answer 2

FMResultSet *result = [db executeQuery: @"SELECT * FROM channels_list WHERE type = 'person' AND members LIKE (?)",[NSString stringWithFormat:@"%%%@%%", userID]];