# Time: O(n^2)

# Space: O(1)

#

# Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything.

#

# Table: Customers.

#

# +----+-------+

# | Id | Name |

# +----+-------+

# | 1 | Joe |

# | 2 | Henry |

# | 3 | Sam |

# | 4 | Max |

# +----+-------+

# Table: Orders.

#

# +----+------------+

# | Id | CustomerId |

# +----+------------+

# | 1 | 3 |

# | 2 | 1 |

# +----+------------+

# Using the above tables as example, return the following:

#

# +-----------+

# | Customers |

# +-----------+

# | Henry |

# | Max |

# +-----------+

#

# Time: O(n^2)

# Space: O(1)

# Write your MySQL query statement below

SELECT Name AS Customers FROM Customers WHERE Id NOT IN (SELECT CustomerId FROM Orders)

# Time: O(n^2)

# Space: O(n)

# Write your MySQL query statement below

SELECT Customers.Name AS Customers FROM (Customers LEFT JOIN Orders ON Customers.Id = Orders.CustomerId) WHERE Orders.CustomerId IS NULL