统一3D中的SQLite本地数据库

Question

I am a new programmer for unity 3D v4.5 pro.I am using unity 3D for my augmented reality application and i have chosen SQLite to create and easily handle with my database (after building it on android). I Found 2 scripts here in java http://wiki.unity3d.com/index.php/SQLite ...I converted it to c#(because i am programming with c#)and it helped me alot but i just couldn't find a method "query" to delete for example only firstName or LastName ..I tried like that :

public void DeleteFrom ( String tableName,String itemToDelete, String wPar,String wValue )
{
    string query ;
    query = "DELETE FROM " + tableName + " WHERE " + itemToDelete + wPar + wValue ;        
    dbcmd = dbcon.CreateCommand();
    dbcmd.CommandText = query;
    reader = dbcmd.ExecuteReader();
}

then i call it in the other script "usethe database" as it is bellow

public void  DeleteRow(string FirstName )
{
    db.DeleteFrom("'"+TableName+"'","FirstName","=","'"+firstName+"'");
}

But what i get is deleting the whole Row ( firstName lastName)

I don't know if you have understand what i mean: i just want to delete firstName and keep in my datatable it's assignment which is lastName so i can assign for that lastName later any other new firstName. I hope you understant my point .Please, i'll appreciate any help and thank you in advance. :)

Answer 1

If I am understanding you correctly, it sounds like you don't want to do an actual delete. There is no such thing as deleting a field, only an entire row. Instead what you want is an Update. Use this code to clear out the first name field of the row:

public void ClearFirstName(string tableName, string firstname )
{
    string query ;
    query = "UPDATE " + tableName + " SET FirstName = '' WHERE FirstName = '" + firstname + "'";        
    dbcmd = dbcon.CreateCommand();
    dbcmd.CommandText = query;
    reader = dbcmd.ExecuteReader();
}

The issue with this code is that once you clear the first name, then you won't be able to reference it a second time (it will be empty). I suggest you add a unique numeric ID field to reference each row in your table. Then you can use that ID in the WHERE clause of your SQL statements.