Builtin

schema

tuple{<attr set>}

A tuple which is the current schema.

So heading(schema){attr} gives the set of variable names in the schema.

Examples

Filter for a given relvar name

heading(schema)[attr="$P"]

attr type

$P {PNO:str,PNAME:str,COLOR:str,WEIGHT:int,CITY:str}

attr	type
$P	{PNO:str,PNAME:str,COLOR:str,WEIGHT:int,CITY:str}

Full example schema

heading(schema)

attr type

$P {PNO:str,PNAME:str,COLOR:str,WEIGHT:int,CITY:str}
$S {SNO:str,SNAME:str,STATUS:int,CITY:str}
$SP {SNO:str,PNO:str,QTY:int}
$constraint {name:str,rule:str}
error {name:str,message:str}

attr	type
$P	{PNO:str,PNAME:str,COLOR:str,WEIGHT:int,CITY:str}
$S	{SNO:str,SNAME:str,STATUS:int,CITY:str}
$SP	{SNO:str,PNO:str,QTY:int}
$constraint	{name:str,rule:str}
error	{name:str,message:str}

Names of variables in the example schema

heading(schema){attr}

attr

$P
$S
$SP
$constraint
error