Hash Comments Work on MySQL and MariaDB and Become an Operator on PostgreSQL

MySQL and MariaDB skip everything from a # to the end of the line. On SQLite and PostgreSQL that # is still part of the statement.

Scripts written for the mysql client often use # comments. SQLite stops with a syntax error. On PostgreSQL # is a bitwise exclusive or, so the rest of the line becomes part of the expression.

What Each Engine Answered

The example

SELECT 1 # one;

gave these answers:

What to Write Instead

This form answers the same on every engine:

SELECT 1 -- one;

Use -- comments, with a space after the dashes, or /* ... */.

What BareSQL Portable Reports

Saved as example.sql, the example gets this from baresql lint --all:

$ baresql lint --all example.sql
example.sql:1:10: error: # starts a comment on MySQL and MariaDB only; SQLite refuses it, and PostgreSQL reads it as the XOR operator. [hash-comment]
    # one;
    Use -- comments, with a space after the dashes, or /* ... */.

1 problem: 1 error.

baresql rules hash-comment prints the same answers in the terminal, and the BareSQL Portable page lists every difference BareSQL knows.