было:
user_id |  tovar_id  | attacker_user_id | tech_id | level
23                   1      45                 101       1
23                   1      45                 102       2
23                   1      45                 103       3
23                   1      45                 104       4

будет:
user_id |  tovar_id  | attacker_user_id | str
23                     1         45                 [{'first':101, 'second':1}, {'first':102, 'second':2}, {'first':103, 'second':3}, {'first':104, 'second':4}]

select user_id ,tovar_id ,attacker_user_id,tech_id || level as str
from tovari