When searching for underscores in Postgresql, literal use of the character _ doesn't work. For example, if you wanted to search all your tables for any columns that ended in _by, for something like change log or activity information, e.g. updated_by, reviewed_by, etc., the following query almost works:
SELECT table_name, column_name FROM information_schema.columns
WHERE column_name LIKE '%_by'
It basically ignores the underscore completely and returns as if you'd searched for LIKE '%by'. This may not be a problem in all cases, but it has the potential to be one. How to search for underscores?
You need to use a backslash to escape the underscore. Change the example query to the following:
SELECT table_name, column_name FROM information_schema.columns
WHERE column_name LIKE '%\_by'
Just ran into the same issue and the single backslash wasn't working as well. I found this documentation on the PostgreSQL community and it worked:
The correct way is to escape the underscore with a backslash. You actually have to write two backslashes in your query:
select * from foo where bar like '%\\_baz'
The first backslash quotes the second one for the query parser, so that what ends up inside the system is %\_baz, and then the LIKE function knows what to do with that.
Therefore use something like this:
SELECT table_name, column_name FROM information_schema.columns
WHERE column_name LIKE '%\\_by'
Source Documentation: https://www.postgresql.org/message-id/10965.962991238%40sss.pgh.pa.us
来源：https://stackoverflow.com/questions/38084864/how-to-escape-underscores-in-postgresql