# Time: O(nlogn)

# Space: O(n)

# Mary is a teacher in a middle school and she has a table seat storing

# students' names and their corresponding seat ids.

#

# The column id is continuous increment.

# Mary wants to change seats for the adjacent students.

# Can you write a SQL query to output the result for Mary?

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

# | id | student |

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

# | 1 | Abbot |

# | 2 | Doris |

# | 3 | Emerson |

# | 4 | Green |

# | 5 | Jeames |

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

#

# For the sample input, the output is:

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

# | id | student |

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

# | 1 | Doris |

# | 2 | Abbot |

# | 3 | Green |

# | 4 | Emerson |

# | 5 | Jeames |

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

#

# Note:

# If the number of students is odd, there is no need to change the last one's seat.

SELECT

s1.id, COALESCE(s2.student, s1.student) AS student

FROM

seat s1

LEFT JOIN

seat s2 ON ((s1.id + 1) ^ 1) - 1 = s2.id

ORDER BY s1.id;