sqlite3 insert and read BLOB data in database

问题

I need to read and write BLOB data to a database. Here is my structure table

    #define CREATE_TABLE_USERS_SQL "CREATE TABLE IF NOT EXISTS %@ ( \
UserID INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, \
Name VARCHAR(50), \
Image BLOB);"

How can I insert it into database, and then retrieve from it?

Environment: iPhone SDK 4.1 SQLite3 database.

This code fails:

        NSData * buf2 = [[NSData alloc] init];
        sqlite3_column_blob(statement, 5);
        buf2 = sqlite3_column_bytes(statement, 5);
        user.image = [UIImage imageWithData: buf2];

回答1:

Thanx all!! With yours help I'v solved problem and want to share results for future beginners like I am.)

-(void) addToDB
{
    NSLog(@"\nCreating db");
    NSString *str = @"CREATE TABLE IF NOT EXISTS Images (image1 BLOB);";
    int res = SQLITE_ERROR;


    res = sqlite3_open([@"aa.sql" UTF8String], &database);
    res = sqlite3_exec(database, [str UTF8String], NULL, NULL, NULL);

    sqlite3_stmt *updStmt =nil; 

    const char *sql = "INSERT INTO Images (image1) VALUES (?);";
    res = sqlite3_prepare_v2(database, sql, -1, &updStmt, NULL);

    if(res!= SQLITE_OK)
    {
        NSLog(@"Error while creating update statement:%s", sqlite3_errmsg(database));
    }

    UIImage *img = [UIImage imageNamed: @"flower.png"];
    NSData *imageData = [NSData dataWithData: UIImagePNGRepresentation(img)];

    res = sqlite3_bind_blob(updStmt, 1, [imageData bytes], [imageData length] , SQLITE_TRANSIENT);

    if((res = sqlite3_step(updStmt)) != SQLITE_DONE)
    {
        NSLog(@"Error while updating: %@", sqlite3_errmsg(database));
        sqlite3_reset(updStmt);
    } 

    res = sqlite3_reset(updStmt);
    res = sqlite3_close(database);
}

-(void) readFromDB
{
    NSLog(@"\nReading from db");

    NSString *query = @"SELECT image1 from Images";
    int res = SQLITE_ERROR;
    int len = 0;

    res = sqlite3_open([@"aa.sql" UTF8String], &database);

    sqlite3_stmt *statement;
    res = sqlite3_prepare_v2 (database, [query UTF8String], -1, &statement, nil);

    if (res == SQLITE_OK)
    {
        if (sqlite3_step(statement) == SQLITE_ROW)
        {
            len = sqlite3_column_bytes(statement, 0);
            NSData *imgData = [[NSData alloc] initWithBytes: sqlite3_column_blob(statement, 0) length: len];           


            UIImage *img = [[UIImage alloc] initWithData:imgData];

            self.view1.image = img;

        }
    }
    sqlite3_finalize(statement);

    res = sqlite3_close(database);
}

回答2:

Apart from choosing your client or programming interface, usage does not differ from any other string field.

[Update] I haven't had the luck to develop for the iPhone yet, but I believe it's the same as any other SELECT or INSERT query. Make sure to encode the BLOB and enclose it with single apostrophes (') like strings.

回答3:

why not use fmdb by Gus Mueller et al, of Flying Meat? http://flyingmeat.com/

https://github.com/ccgus/fmdb

If you find fmdb useful, go and buy one of the excellents apps of Flying Meat. VoodooPad or Acron.

回答4:

//-----insert IMAGE

  - (void)setImage:(UIImage *)theImage
 {

  if(sqlite3_open([databasePath UTF8String],&myDatabase)==SQLITE_OK)
  {    
    NSString *insertProgrammeSql = @"INSERT INTO imageTable (imageName) VALUES (?)";

sqlite3_stmt *statement;

   if (sqlite3_prepare_v2(myDatabase, [insertProgrammeSql cStringUsingEncoding:NSUTF8StringEncoding], -1, &statement, NULL) == SQLITE_OK) {

    NSData *imageData = UIImagePNGRepresentation(theImage);

         sqlite3_bind_blob(statement, 1, [imageData bytes], [imageData length], SQLITE_TRANSIENT);

    sqlite3_step(statement);
}
  sqlite3_close(myDatabase);
//  return YES;    
}   


  }

//--------get image

   -(UIImage *)getImage

    {

    UIImage *image = nil;


if(sqlite3_open([databasePath UTF8String],&myDatabase)==SQLITE_OK)
{   

NSString *selectSql = @"SELECT image FROM imageTable";

sqlite3_stmt *statement;
if (sqlite3_prepare_v2(myDatabase, [selectSql UTF8String], -1, &statement, NULL) == SQLITE_OK)
{
    int length = sqlite3_column_bytes(statement, 0);
    NSData *imageData = [NSData dataWithBytes:sqlite3_column_blob(statement, 0 ) length:length];

    image = [UIImage imageWithData:imageData];



  sqlite3_finalize(statement);

  }
     sqlite3_close(myDatabase);
  }
 return image;
 }

回答5:

This code fails:

   NSData * buf2 = [[NSData alloc] init];
   sqlite3_column_blob(statement, 5);
   buf2 = sqlite3_column_bytes(statement, 5);
   user.image = [UIImage imageWithData: buf2];

You are calling the SQLite functions in the correct order. According to the SQLite docs:

The safest and easiest to remember policy is to invoke these routines in one of the following ways:

sqlite3_column_text() followed by sqlite3_column_bytes()

sqlite3_column_blob() followed by sqlite3_column_bytes()

sqlite3_column_text16() followed by sqlite3_column_bytes16()

In other words, you should call sqlite3_column_text(), sqlite3_column_blob(), or sqlite3_column_text16() first to force the result into the desired format, then invoke sqlite3_column_bytes() or sqlite3_column_bytes16() to find the size of the result. Do not mix calls to sqlite3_column_text() or sqlite3_column_blob() with calls to sqlite3_column_bytes16(), and do not mix calls to sqlite3_column_text16() with calls to sqlite3_column_bytes().

However, buff2 is an integer, not a data pointer. sqlite3_column_bytes tells you how many bytes are in the blob.

来源：https://stackoverflow.com/questions/4215505/sqlite3-insert-and-read-blob-data-in-database

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