1NF is the First Normal Form. It is the simplest type of normalization that you can implement in a database. The primary objectives of 1NF are to:

    - Every column must have atomic (single value)
    - To Remove duplicate columns from the same table
    - Create separate tables for each group of related data and identify each row with a unique column

Explain 1NF (first normal form)?

The so called "N + 1 problem" is an issue that occurs when code needs to load the children of a parent-child relationship with a ORMs that have lazy-loading enabled, and that therefore issue a query for the parent record, and then one query for each child record. How to fix it?

Let's say you have a collection of Car objects (database rows), and each Car has a collection of Wheel objects (also rows). In other words, Car → Wheel is a 1-to-many relationship.

Now, let's say you need to iterate through all the cars, and for each one, print out a list of the wheels. The naive O/R implementation would do the following:

```
SELECT * FROM Cars;
```
And then for each Car:

```
SELECT * FROM Wheel WHERE CarId = ?
```

In other words, you have one select for the Cars, and then N additional selects, where N is the total number of cars.

Alternatively, one could get all wheels and perform the lookups in memory:

```
SELECT * FROM Wheel;
```

This reduces the number of round-trips to the database from N+1 to 2. Most ORM tools give you several ways to prevent N+1 selects specially using JOINs.



Top Database Interview Questions

1. Explain 1NF (first normal form)?

2. What is N+1 Problem?