更新数据库（SQLiteDatabase问题）

Question

everyone. This is a piece of code from using sqlite in android tutorial:

return db.update(employeeTable, cv, colID+"=?", 
new String []{String.valueOf(emp.getID())});  

I don't understand why in colID+"=?" after '=' stay '?'

Anyone can explain this, please?

Thanks for everyone!

Answer 1

This is parametrized statement, this mean that this String.valueOf(emp.getID()) will be added intead of ? character. ? represents one argument and String[] represents data which will be added to where clause.

Answer 2

The ? is where your argument is substituted into the query. Your argument in this case is String.valueOf(emp.getID() .

Answer 3

This is a Prepared Satatement. In this case, you can define a query as a template and left some parameters to fill dynamically. You represent the parameter with an ? . In your case, you are indicating that String.valueOf(emp.getID()) will substitute the ? .