dealing with existing data applied to nestedset

[omarIbrahim2]

i have a project which has tables and data exist when i set up migration needed in nestedset package _lft and _rgt default is 0
when i try to update the data and create childrens and reconstruct the the tree
this error appeared
SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '0 else _lft end, _rgt = case when _rgt between 2 and 1 then _rgt-1 wh...' at line 1
how can i solve this problem ?