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create table bal(Perevod varchar(40))
✓
insert into bal values('aaa/dddd')
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UPDATE bal
SET Perevod = substr(Perevod, 1, INSTR(Perevod, '/')-1)
WHERE INSTR(Perevod, '/')>0;
✓
select *
from bal
| Perevod |
|---|
| aaa |