Golang Insert NULL into sql instead of empty string

Question

I\'m trying to insert data into a mysql database using golang. In the case where my value takes on an empty string, I would want to insert a null. How can I adjust the following

Answer 1

The database/sql package has a NullString type (docs) for just this situation.

Basically just use sql.NullString in place of strings where you want them to be nullable in db.

You could also use a *string in your code to the same effect.

The problem in either case is in mapping to/from a nullable string to a non-nullable string. The empty string is technically a value, so you will almost always have to do something like this if you decide empty string should be translated to nil:

nullableS := &s
if s == "" {
  nullableS = nil
}

The alternative would be to just use *string instead of string in your models throughout your app.

In databases, I have been taking the approach that empty string and null are equivalent, and just storing empty sting in the db, and making most columns non-nullable.

Answer 2

In my code I have a function that converts a string to sql.NullString

func NewNullString(s string) sql.NullString {
    if len(s) == 0 {
        return sql.NullString{}
    }
    return sql.NullString{
         String: s,
         Valid: true,
    }
}

Then whenever I am using Exec I wrap my strings that could be NULL in the DB with the NewNullString function.

db.Exec(`
  insert into
      users first_name, last_name, email
      values (?,?,?)`,
  firstName,
  lastName,
  NewNullString(email),
)