Week                                    Contract
emp_id | starting   | data1 |  ...   emp_id | from_date  | data2 | ...
-------|------------|-------|--      -------|------------|-------|--
12     | 2019-01-08 | abcd  |        12     | 2018-08-01 | efgh  |
12     | 2019-01-15 | abcd  |        13     | 2018-10-02 | efgh  |
12     | 2019-01-22 | abcd  |        13     | 2018-01-15 | ijkl  |
13     | 2019-01-08 | abcd  |        13     | 2018-03-19 | mnop  |
13     | 2019-01-15 | abcd  |        14     | 2017-02-02 | efgh  |
13     | 2019-01-22 | abcd  |        15     | 2018-01-19 | efgh  |

SELECT * FROM contract
WHERE contract.emp_id = @emp_id AND contract.from_date <= @starting
ORDER BY contract.from_date DESC
LIMIT 1

emp_id | starting   | from_date  | data1 | data2 | ...
-------|------------|------------|-------|-------|--
12     | 2019-01-08 | 2018-08-01 | abcd  | efgh  |
12     | 2019-01-15 | 2018-08-01 | abcd  | efgh  |
12     | 2019-01-22 | 2018-08-01 | abcd  | efgh  |
13     | 2019-01-08 | 2018-10-02 | abcd  | efgh  |
13     | 2019-01-15 | 2019-01-15 | abcd  | ijkl  |
13     | 2019-01-22 | 2019-01-15 | abcd  | ijkl  |