Select all employee's name and bonus whose bonus is < 1000.

Table:Employee

+-------+--------+-----------+--------+

| empId |  name  | supervisor| salary |

+-------+--------+-----------+--------+

|   1   | John   |  3        | 1000   |

|   2   | Dan    |  3        | 2000   |

|   3   | Brad   |  null     | 4000   |

|   4   | Thomas |  3        | 4000   |

+-------+--------+-----------+--------+

empId is the primary key column for this table.

Table: Bonus

+-------+-------+

| empId | bonus |

+-------+-------+

| 2     | 500   |

| 4     | 2000  |

+-------+-------+

empId is the primary key column for this table.

Example ouput:

+-------+-------+

| name  | bonus |

+-------+-------+

| John  | null  |

| Dan   | 500   |

| Brad  | null  |

+-------+-------+

Code

SELECT e.name, b.bonus FROM Employee as e LEFT JOIN Bonus as b ON e.empId = b.empId WHERE b.bonus IS NULL or b.bonus < 1000

# 不能直接用JOIN, 相当于inner join, 如果bonus没有的, 那么就没有了, 所以上面的例子只会输出Dan, 500 这一栏而已.