Cannot parse Oracle's MINUS without specifying the dialect

[la1ty]

The MINUS operation in Oracle SQL is equivalent to the EXCEPT in SQL.

Fully reproducible code snippet

import sqlglot

sqlglot.parse_one('select 1 from dual minus select 2 from dual')

[VaggelisD]

Any reason not to specify the dialect? I see that MINUS is also used in other dialects so possibly it could become supported in the base dialect but SQLGlot does not guarantee any behavior if the dialect is not passed.

Happy to continue discussing but closing this PR for now.

[la1ty]

Any reason not to specify the dialect? I see that MINUS is also used in other dialects so possibly it could become supported in the base dialect but SQLGlot does not guarantee any behavior if the dialect is not passed.

I'm developing a text-to-sql application, which uses LLM to generate SQLs. Before executing SQL, I need to validate the SQL syntax and add the corresponding permission control information. Currently, I use sqlglot to handle this part of work.

However, one of our database server is an old version, Oracle 11g, which is not compatible with sqlglot's oracle dialect. If I specify dialect to oracle, some operation will be transpiled to a new form that Oracle 11g does not support.

I've tested sqlglot with hundreds of SQLs without specifying a dialect and it works well, until I find out that sqlglot does not support the MINUS operation. Since sqlglot support the EXCEPT operation and the MINUS operation is just a synonym of EXCEPT, adding MINUS support should be not hard. What's more, it can improve sqlglot's compatibility with general SQL syntax parsing.