spanner nullable data type
```
// NullableValue is the interface implemented by all null value wrapper types.
type NullableValue interface {
// IsNull returns true if the underlying database value is null.
IsNull() bool
}
```
- how to use
- difference between null,"","someValue"
- null
- spanner.NullString(valid=false)
- ""
- spanner.NullString(valid=true,value="")
- update(value[*NullableValue]->model[NullableValue])
- update target items
- value is not nil
- not update target items
- value is nil
- vo is all pointer
by the way, another orm tool,gorm , don't solve this problem well.
var user User
db.First(&user)
db.Model(&user).Updates(User{Age: 18, Name: nil})
// 実行 SQL : UPDATE `users` SET `age` = '18' WHERE `users`.`id` = '1'
GORM のドキュメントを見ると以下のように書いてあったので、構造体で実行すると無視されてしまうようです。 When query with struct, GORM will only query with those fields has non-zero value,
that means if your field's value is 0, '', false or other zero values,
it won't be used to build query conditions,