如何在iphone应用程序中获取数据时在sqlite查询中传递变量

Question

我从sqlite表获取数据,我想传递变量,以便如果sub_Catgeory等于该变量,那么它应该获取记录.

  const char *sql = "select * from category where sub_Category=appDelegate.sub_Category";

同样如果不使用appDelegate.Sub_Category变量那么它工作正常

  const char *sql = "select * from category where sub_Category='Glucagon'";

我的完整代码

   + (void) getInitialData:(NSString *)dbPath {

     MultipleDetailViewsWithNavigatorAppDelegate *appDelegate = (MultipleDetailViewsWithNavigatorAppDelegate *)[[UIApplication sharedApplication] delegate];

     if (sqlite3_open([dbPath UTF8String], &database) == SQLITE_OK) {

        //const char *sql = "select * from category where sub_Category='Glucagon'";

       NSLog(@"Sub Category is %@",appDelegate.subCategory);

       const char *sql = "select * from category where sub_Category='appDelegate. subcategory'";

       sqlite3_stmt *selectstmt;
       if(sqlite3_prepare_v2(database, sql, -1, &selectstmt, NULL) == SQLITE_OK {

         while(sqlite3_step(selectstmt) == SQLITE_ROW) {

            NSInteger primaryKey = sqlite3_column_int(selectstmt, 0);
            Coffee *coffeeObj = [[Coffee alloc] initWithPrimaryKey:primaryKey];
            coffeeObj.category=sqlite3_column_int(selectstmt,1);
            coffeeObj.sub_Category = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 2)];
            coffeeObj.content_Type = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 3)];
            coffeeObj.content_Title = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt,4)];

            coffeeObj.publisher = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 5)];
            coffeeObj.content_Description = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 6)];
            coffeeObj.content_Id = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 7)];
            coffeeObj.content_Source = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 8)];

            int count=[appDelegate.arrayOneC count];

            NSLog(@"count is beofore getting values %d",count);

            [appDelegate.arrayOneC addObject:coffeeObj];

            int countone=[appDelegate.arrayOneC count];

            NSLog(@"count is after getting values %d",countone);

            [coffeeObj release];
        }
    }
}
else
    sqlite3_close(database); //Even though the open call failed, close the database connection to release all the memory.
}

Answer 1

你可以这样做,

假设你已经宣布了static sqlite3_stmt *selectStmt = nil;一些地方

const char *sqlStatement = "select * from category where sub_Category=?";

if(sqlite3_prepare_v2(database, sqlStatement, -1, &selectStmt, NULL) == SQLITE_OK) 
{
    sqlite3_bind_text(selectStmt, 1, [appDelegate.sub_Category  UTF8String], -1, SQLITE_TRANSIENT);
    while(sqlite3_step(selectStmt) == SQLITE_ROW) 
    {
            //Process data
    }
}

//Reset the select statement.
sqlite3_reset(selectStmt);
selectStmt = nil;

它被称为准备语句的绑定值.点击此处查看更多详细信息.

编辑 - 见下面编辑的功能.

+(void)getInitialData:(NSString *)dbPath
{
    MultipleDetailViewsWithNavigatorAppDelegate *appDelegate = (MultipleDetailViewsWithNavigatorAppDelegate *)[[UIApplication sharedApplication] delegate];
    if (sqlite3_open([dbPath UTF8String], &database) == SQLITE_OK)
    {
        NSLog(@"Sub Category is %@",appDelegate.subCategory);
        const char *sql = "select * from category where sub_Category=?";
        sqlite3_stmt *selectstmt;
        if(sqlite3_prepare_v2(database, sql, -1, &selectstmt, NULL) == SQLITE_OK)
        {
            sqlite3_bind_text(selectStmt, 1, [appDelegate.sub_Category  UTF8String], -1, SQLITE_TRANSIENT);
            while(sqlite3_step(selectstmt) == SQLITE_ROW)
            {
                NSInteger primaryKey = sqlite3_column_int(selectstmt, 0);
                Coffee *coffeeObj = [[Coffee alloc] initWithPrimaryKey:primaryKey];
                coffeeObj.category=sqlite3_column_int(selectstmt,1);
                coffeeObj.sub_Category = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 2)];
                coffeeObj.content_Type = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 3)];
                coffeeObj.content_Title = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt,4)];
                coffeeObj.publisher = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 5)];
                coffeeObj.content_Description = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 6)];
                coffeeObj.content_Id = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 7)];
                coffeeObj.content_Source = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 8)];
                int count=[appDelegate.arrayOneC count];
                NSLog(@"count is beofore getting values %d",count);
                [appDelegate.arrayOneC addObject:coffeeObj];
                int countone=[appDelegate.arrayOneC count];
                NSLog(@"count is after getting values %d",countone);
                [coffeeObj release];
            }
        }
    }
    else
        sqlite3_close(database);
}

Answer 2

试试这个.

第一路.

NSString *queryString = [NSString stringWithFormat:@"select * from category where sub_Category='%@'", appDelegate.subCategory];
const char *sqlQuery = [queryString UTF8String];

     if(sqlite3_prepare_v2(database, sqlQuery, -1, &selectStatement, NULL) == SQLITE_OK){
                while (sqlite3_step(selectStatement) == SQLITE_ROW){
    //Fetching your data logic
    }
}

第二种方式.

const char *sqlStatement = "select * from category where sub_Category=?";

if(sqlite3_prepare_v2(database, sqlStatement, -1, &selectStmt, NULL) == SQLITE_OK) 
{
    sqlite3_bind_text(selectStmt, 1, [appDelegate.subCategory  UTF8String], -1, SQLITE_TRANSIENT);
    while(sqlite3_step(selectStmt) == SQLITE_ROW) 
    {
            //Process data
    }
}

谢谢HarshIT,rmaddy和Jennis.