Builtin

wrap

wrap(a, {attr_list}, wrap_name)

A relation operator. Adds a new nested tuple, named wrap_name, containing each attr in the attr list moved down from a.

Examples

wrap

wrap($S, {SNO, SNAME, CITY}, sups)

STATUS sups

10 CITY
Paris
SNAME
Jones
SNO
S2
20 CITY
London
SNAME
Smith
SNO
S1
20 CITY
London
SNAME
Clark
SNO
S4
30 CITY
Paris
SNAME
Blake
SNO
S3
30 CITY
Athens
SNAME
Adams
SNO
S5

STATUS	sups
10	CITY Paris SNAME Jones SNO S2
20	CITY London SNAME Smith SNO S1
20	CITY London SNAME Clark SNO S4
30	CITY Paris SNAME Blake SNO S3
30	CITY Athens SNAME Adams SNO S5

wrap with inverted attr_list

wrap($S, ~{STATUS}, sups)

STATUS sups

10 CITY
Paris
SNAME
Jones
SNO
S2
20 CITY
London
SNAME
Smith
SNO
S1
20 CITY
London
SNAME
Clark
SNO
S4
30 CITY
Paris
SNAME
Blake
SNO
S3
30 CITY
Athens
SNAME
Adams
SNO
S5

STATUS	sups
10	CITY Paris SNAME Jones SNO S2
20	CITY London SNAME Smith SNO S1
20	CITY London SNAME Clark SNO S4
30	CITY Paris SNAME Blake SNO S3
30	CITY Athens SNAME Adams SNO S5

Note: this version gives the same results as above but behaves as expected if new attributes are added to the relation (and perhaps reads more easily).