CODEWITHSUNDEEP
sqlcomments
ojblass
ojblass

Reputation: 21620

Are there multiline comment delimiters in SQL that are vendor-agnostic?

While editing, building up, or cherry picking from SQL statements I can find myself interacting with one of four popular database tools.

I have been resorting to single line commenting for DB2 and Informix. I have created macros in Vim to make this slightly more efficient, but I was wondering if I am working too hard.

Upvotes: 38

Views: 20861

Answers (2)

Jonathan Leffler
Jonathan Leffler

Reputation: 753970

C style comments are standard in SQL 2003 and SQL 2008 (but not in SQL 1999 or before). The following DBMS all support C style comments:

  • Informix
  • PostgreSQL
  • MySQL
  • Oracle
  • DB2
  • Sybase
  • Ingres
  • Microsoft SQL Server
  • SQLite (3.7.2 and later)
  • Teradata and Aster

That is not every possible DBMS, but it is more or less every major SQL DBMS. (I'll willingly add notes about any other DBMS that does - or does not - support C style comments.)

The SQL 2003 standard documents comment notations thus:

<comment> ::= <simple comment> | <bracketed comment>

<simple comment> ::=
    <simple comment introducer> [ <comment character> ... ] <newline>

<simple comment introducer> ::=
    <minus sign> <minus sign> [ <minus sign> ... ]

<bracketed comment> ::=
    <bracketed comment introducer> <bracketed comment contents>
    <bracketed comment terminator>

<bracketed comment introducer> ::= <slash> <asterisk>

<bracketed comment terminator> ::= <asterisk> <slash>

<bracketed comment contents> ::= [ { <comment character> | <separator> }... ]

<comment character> ::= <nonquote character> | <quote>

IBM Informix Dynamic Server (IDS or Informix) supports C style comments. It also supports '{ ... }' as potentially multi-line comments, except in contexts where it means something else - that something else being a LIST or SET or MULTISET literal. (You might find that DB-Access gets confused by C style comments; that is a separate issue.)

Upvotes: 45

Ben Hoffstein
Ben Hoffstein

Reputation: 103345

The ISO standard only defines single-line comments beginning with two dashes. Some vendors support C-style commenting (i.e. multiline beginning with /* and ending with */), but it should not be considered "vendor agnostic".

Upvotes: 9

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