add support for odbc scalar exprs

Language/SQL/SimpleSQL/Parse.lhs

@@ -1104,6 +1104,25 @@ separate suffix.
 >     i <- names
 >     pure $ \v -> Collate v i
 
+== odbc syntax
+
+the parser supports three kinds of odbc syntax, two of which are
+scalar expressions (the other is a variation on joins)
+
+
+> odbcExpr :: Parser ValueExpr
+> odbcExpr = between (symbol "{") (symbol "}")
+>            (odbcTimeLit <|> odbcFunc)
+>   where
+>     odbcTimeLit =
+>         OdbcLiteral <$> choice [OLDate <$ keyword "d"
+>                                ,OLTime <$ keyword "t"
+>                                ,OLTimestamp <$ keyword "ts"]
+>                     <*> singleQuotesOnlyStringTok
+>     -- todo: this parser is too general, the expr part
+>     -- should be only a function call (from a whitelist of functions)
+>     -- or the extract operator
+>     odbcFunc = OdbcFunc <$> (keyword "fn" *> valueExpr)
 
 ==  operators
 
@@ -1254,7 +1273,8 @@ documenting/fixing.
 >               ,subquery
 >               ,intervalLit
 >               ,specialOpKs
->               ,idenExpr]
+>               ,idenExpr
+>               ,odbcExpr]
 >        <?> "value expression"
 
 expose the b expression for window frame clause range between

Language/SQL/SimpleSQL/Pretty.lhs

@@ -227,6 +227,16 @@ which have been changed to try to improve the layout of the output.
 > valueExpr d (VEComment cmt v) =
 >     vcat $ map comment cmt ++ [valueExpr d v]
 
+> valueExpr _ (OdbcLiteral t s) =
+>     text "{" <> lt t <+> quotes (text s) <> text "}"
+>   where
+>     lt OLDate = text "d"
+>     lt OLTime = text "t"
+>     lt OLTimestamp = text "ts"
+
+> valueExpr d (OdbcFunc e) =
+>     text "{fn" <+> valueExpr d e <> text "}"
+
 > unname :: Name -> String
 > unname (Name Nothing n) = n
 > unname (Name (Just (s,e)) n) =

Language/SQL/SimpleSQL/Syntax.lhs

@@ -19,6 +19,7 @@
 >     ,Frame(..)
 >     ,FrameRows(..)
 >     ,FramePos(..)
+>     ,OdbcLiteralType(..)
 >      -- * Query expressions
 >     ,QueryExpr(..)
 >     ,makeSelect
@@ -215,6 +216,10 @@ in other places
 >     | MultisetQueryCtor QueryExpr
 >     | NextValueFor [Name]
 >     | VEComment [Comment] ValueExpr
+>     | OdbcLiteral OdbcLiteralType String
+>       -- ^ an odbc literal e.g. {d '2000-01-01'}
+>     | OdbcFunc ValueExpr
+>       -- ^ an odbc function call e.g. {fn CHARACTER_LENGTH('test')}
 >       deriving (Eq,Show,Read,Data,Typeable)
 
 > -- | Represents an identifier name, which can be quoted or unquoted.
@@ -304,6 +309,15 @@ not sure if scalar subquery, exists and unique should be represented like this
 >               | UnboundedFollowing
 >                 deriving (Eq,Show,Read,Data,Typeable)
 
+
+> -- | the type of an odbc literal (e.g. {d '2000-01-01'}),
+> -- correpsonding to the letter after the opening {
+> data OdbcLiteralType = OLDate
+>                      | OLTime
+>                      | OLTimestamp
+>                        deriving (Eq,Show,Read,Data,Typeable)
+
+
 > -- | Represents a query expression, which can be:
 > --
 > -- * a regular select;