How to escape underscores in Oracle SQL Developer?

You need to use the explicit escape; in this way you can decide a character to use for escaping and then use it in your LIKE.

For example, here I use the '!' to escape special characters:

select str
from (
        select 'a_b' str from dual union all
        select 'ab'      from dual
     )
where str like '%!_%' escape '!'

gives

STR
---
a_b

Oracle suggests the code below which workded for me:

SELECT last_name 
    FROM employees
    WHERE last_name LIKE '%A\_B%' ESCAPE '\'
    ORDER BY last_name;

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