Is whitespace optional in SQL queries?

I have noticed that using either Oracle or SQLite, queries like this are perfectly valid

SELECT*FROM(SELECT a,MAX(b)i FROM c GROUP BY a)WHERE(a=1)OR(i=2);

Is that a “feature” of SQL that keywords or words of a query need not be surrounded with whitespace? If so, why was it designed this way? SQL has been design开发者_运维问答ed to be readable, this seems to be a form of obfuscation (particularly the MAX(b)i thing where i is a token which serves as an alias).

SQL-92 BNF Grammar here explicitly states that delimiters (bracket, whitespace, * etc) are valid to break up the tokens, which makes the white space optional in various cases where other delimiters already break up the tokens.

This is true not only for SQLite and Oracle, but MySQL and SQL Server at least (that I work with and have tested), since it is specified in the language definition.

Whitespace is optional in pretty much any language where it is not absolutely necessary to preserve boundaries between keywords and/or identifiers. You could write code in C# that looked similar to your SQL, and as long as the compiler can still parse the identifiers and keywords, it doesn't care.

Case in point: The subquery of your statement is the only place where whitespace is needed to separate keywords from other alpha characters. Everywhere else, some non-alphanumeric character (which aren't part of any keyword in SQL) separates keywords, so the SQL parser can still digest this statement. As long as that is true, whitespace is purely for human readability.

Most of this is valid simply because you've enclosed key sections in parentheses where white space would ordinarily be required.

I think this is a side effect of the parser.

Usually the compilers will ignore white spaces via blocks SKIP, which are tokens ignored by the compiler but that cause errors if in the middle of a reserved word. For example in C: 'while' is valid, 'whi le' is not although the whitespace is a SKIP token.

The reason is that it simplifies the parser, if not they would have to manage all the white space and that can be quite complex unless you set strict rules like Python does, but that would be both hard to impose to vendors like Oracle and would make SQL more complex than it should.

And that simplification has the (unintended?) side effect of being able to remove MOST (not all) white spaces. Be aware in some cases the removal of white spaces may cause compilation errors (can't remove the space in GROUP BY as that's part of the token).