urQL/docs/in-progress/ref-ch05-query.md

QUERY

The full syntax involves complex manipulations at the row level through scalar functions, data aggregation across preliminary rows via aggregate functions, filtering by aggregation, and row ordering.

NOTE: scalar and aggregate functions are currently under development and not available. Also, these are subject to change.

<scalar-function> ::=
  IF <predicate> THEN { <expression> | <scalar-function> }
                 ELSE { <expression> | <scalar-function> } ENDIF
  | CASE <expression>
    WHEN { <expression> | <predicate> }
	  THEN { <expression> | <scalar-function> } [ ...n ]
    [ ELSE { <expression> | <scalar-function> } ]
    END
  | COALESCE ( <expression> [ ,...n ] )
  | <arithmetic>
  | <bitwise>
  | <predicate>
  | <boolean>
  | <scalar>

If a CASE expression uses <predicate>, the expected boolean (or loobean) logic applies. If it uses <expression> @0 is treated as false and any other value as true (not loobean). (NOTE: This is preliminary design subject to change.)

COALESCE returns the first <expression> in the list that exists. Non-existence occurs when a selected <expression> value is not returned due to an outer join not matching or <scalar-query> not returning rows.

See CH 8 Functions for full documentation on Scalars.

<expression> ::=
  { ...
    | <aggregate-function>( { <column> | <scalar> } )
  }

<aggregate-function> ::=
  { AVG | MAX | MIN | SUM | COUNT | AND | OR | <user-defined> }