iOS - 使用 sqlite 数据库更新数据不起作用

Question

我想更新 Xcode sqlite db 中的一些数据。 db连接成功，但是sql语句好像有问题，一直返回“添加联系人失败”，谢谢帮助。

- (void) saveData:(id)sender
{

    NSLog(@"The code runs through here!");
    sqlite3_stmt    *statement;

    NSString *documents = [self applicationDocumentsDirectory];
    NSString *dbPath = [documents stringByAppendingPathComponent:@"monitorDB.sqlite"];
    const char *dbpath = [dbPath cStringUsingEncoding:NSASCIIStringEncoding];

    if (sqlite3_open(dbpath, & contactDB) == SQLITE_OK)
    {

        NSString *insertSQL = [NSString stringWithFormat:
                               @"UPDATE profile SET username = \"%@\" WHERE id = 1" ,
                               self.username.text];

        const char *insert_stmt = [insertSQL UTF8String];
        sqlite3_prepare_v2(contactDB, insert_stmt,
                           -1, &statement, NULL);
        if (sqlite3_step(statement) == SQLITE_DONE)
        {
            self.settingStatus.text = @"Contact added";
        } else {
            self.settingStatus.text = @"Failed to add contact";
        }
        sqlite3_finalize(statement);
        sqlite3_close(contactDB);
    }   else {
        self.settingStatus.text = @"DB Not Connect";
    }



}

Answer 1

像这样试试..

在 viewdidload 中，我们需要检查表是否存在。如果没有，我们需要创建 db。

NSString *docsdir;
NSArray *dirpaths;

dirpaths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsdir=[dirpaths objectAtIndex:0];
dabasePath=[NSString stringWithFormat:[docsdir stringByAppendingPathComponent:@"contact.db"]];

NSFileManager *filemgr= [NSFileManager defaultManager];
if ([filemgr fileExistsAtPath:dabasePath]==NO ) {
    const char *dbpath=[dabasePath UTF8String];
    if (sqlite3_open(dbpath, &contactDB)== SQLITE_OK) {
        char *error;
        const char *sql_stmt="CREATE TABLE IF NOT EXISTS CONTACTS (ID INTEGER PRIMARY KEY AUTOINCREMENT, ADDRESS TEXT, NAME TEXT, PHONE TEXT, IMAGE BLOB)";
        if (sqlite3_exec(contactDB, sql_stmt, NULL, NULL, &error)!= SQLITE_OK) {
            status.text=@"failed to create";
        }
        sqlite3_close(contactDB);
    }
}

要保存数据，请尝试使用以下代码。

-(IBAction)saveData:(id)sender{

    sqlite3_stmt *statement;
    const char *dbpath = [dabasePath UTF8String];
    NSData *imagedata=UIImagePNGRepresentation(imageview.image);
    if (sqlite3_open(dbpath, &contactDB) == SQLITE_OK) {
        NSString *insertSql =[NSString stringWithFormat:@"INSERT INTO CONTACTS (name, address, phone, image) VALUES (\"%@\", \"%@\", \"%@\", ?) ", name.text, address.text, phone.text ];
        // NSString *nam=name.text;
        const char *insert_stmt = [insertSql UTF8String];
        sqlite3_prepare_v2(contactDB, insert_stmt, -1, &statement, NULL);
        sqlite3_bind_blob(statement, 1, [imagedata bytes], [imagedata length], NULL);

        if (sqlite3_step(statement) == SQLITE_DONE) {
          status.text=@"contact added";
          [self clearClick:nil];
        }else{
          status.text=@"failed to added";
        }
        sqlite3_finalize(statement);
        sqlite3_close(contactDB);
    }
}

要更新数据，请尝试使用以下代码。

-(IBAction)updateClick:(id)sender{

sqlite3_stmt *updateStmt;
 const char *dbpath = [dabasePath UTF8String];
if(sqlite3_open(dbpath, &contactDB) == SQLITE_OK)
{
    const char *sql = "update contacts Set address = ?, phone = ?, image = ? Where name=?";
    if(sqlite3_prepare_v2(contactDB, sql, -1, &updateStmt, NULL)==SQLITE_OK){
        sqlite3_bind_text(updateStmt, 4, [name.text UTF8String], -1, SQLITE_TRANSIENT);
        sqlite3_bind_text(updateStmt, 1, [address.text UTF8String], -1, SQLITE_TRANSIENT);
        sqlite3_bind_text(updateStmt, 2, [phone.text UTF8String], -1, SQLITE_TRANSIENT);
        NSData *imagedata=UIImagePNGRepresentation(imageview.image);
        sqlite3_bind_blob(updateStmt, 3, [imagedata bytes], [imagedata length], NULL);
    }
}
char* errmsg;
sqlite3_exec(contactDB, "COMMIT", NULL, NULL, &errmsg);

if(SQLITE_DONE != sqlite3_step(updateStmt)){
    NSLog(@"Error while updating. %s", sqlite3_errmsg(contactDB));
}
else{
    [self clearClick:nil];
}
sqlite3_finalize(updateStmt);
sqlite3_close(contactDB);
}

Answer 2

检查您的 sql 查询并像这样更改它。

NSString *insertSQL = [NSString stringWithFormat:
                           @"UPDATE profile SET username = '%@' WHERE id = 1" ,
                           self.username.text];

或者如果你想使用绑定文本。

if (sqlite3_open(dbpath, & contactDB) == SQLITE_OK)
{    
    const char *insert_stmt = "UPDATE profile SET username = ? WHERE id = 1";
    if(sqlite3_prepare_v2(contactDB, insert_stmt,
                          -1, &statement, NULL)== SQLITE_OK)
    {
        sqlite3_bind_text(statement, 1, [self.username.text UTF8String], -1, SQLITE_TRANSIENT);
    }

    if (sqlite3_step(statement) == SQLITE_DONE)
    {
        self.settingStatus.text = @"Contact added";
    } else {
        self.settingStatus.text = @"Failed to add contact";
    }
    sqlite3_finalize(statement);
    sqlite3_close(contactDB);
}   else {
    self.settingStatus.text = @"DB Not Connect";
}

Answer 3

检查一下

   in .h file NSString *databaseName;
            NSString *databasePath;

        and in .m file specify  databaseName = @"Db name";
    NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDir = [documentPaths objectAtIndex:0];
    databasePath = [documentsDir stringByAppendingPathComponent:databaseName];

            -(void)save:(id)sender
                {
                    [self checkAndCreateDatabase];
                    sqlite3 *contactDB;
                    sqlite3_stmt *updateStmt;

                    if(sqlite3_open([databasePath UTF8String], &contactDB) == SQLITE_OK)
                    {
                        NSString *querySql=[NSString stringWithFormat:
                                           @"UPDATE profile SET username = \"%@\" WHERE id = 1" ,
                                           self.username.text];
                        const char*sql=[querySql UTF8String];
                        if(sqlite3_prepare_v2(contactDB,sql, -1, &updateStmt, NULL) == SQLITE_OK)
                        {
                            if(SQLITE_DONE != sqlite3_step(updateStmt))
                            {
                                NSLog(@"Error while updating. '%s'", sqlite3_errmsg(contactDB));
                            }
                            else{
                                sqlite3_reset(updateStmt);
                                NSLog(@"Update done successfully!");
                            }
                        }

                        sqlite3_finalize(updateStmt);
                    }
                    sqlite3_close(contactDB);
                }


                -(void) checkAndCreateDatabase{

                    BOOL success;
                    NSFileManager *fileManager = [NSFileManager defaultManager];
                    success = [fileManager fileExistsAtPath:databasePath];
                    if(success) return;

                    NSString *databasePathFromApp = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:databaseName];
                    [fileManager copyItemAtPath:databasePathFromApp toPath:databasePath error:nil];

                }

Answer 4

有很多可能性请检查以下所有内容：

1) 用 nil 初始化语句

sqlite3_stmt    *statement = nil;

2) 在下面试试

if (sqlite3_prepare_v2(contactDB, insert_stmt,-1, &statement, NULL) == SQLITE_OK)
{
 while (sqlite3_step(statement) == SQLITE_ROW)
 {
   //Updated
 }
}
else
{
    NSLog(@"error is %s",sqlite3_errmsg(database));
}

Answer 5

您确定 dbPath 不在应用程序包中吗？我们无法更新包中的 db。

sqlite3_prepare_v2() and sqlite3_step() will return an int.

你可以在 sqlite3.h 中找到你想要的东西。

Like #define SQLITE_BUSY         5   /* The database file is locked */ ...

还有，为什么不使用 FMDB？你可以在 Github 上轻松找到它。 （链接https://github.com/ccgus/fmdb）