Functions for structures

ExpandStruct

Adding one or more new fields to the structure.

If the field set contains duplicate values, an error is returned.

Arguments:

• The first argument passes the source structure to be expanded.
• All the other arguments must be named, each argument adds a new field and the argument's name is used as the field's name (as in AsStruct).

Examples

$struct = AsStruct(1 AS a);
SELECT
  ExpandStruct(
    $struct,
    2 AS b,
    "3" AS c
  ) AS abc;

AddMember

Adding one new field to the structure. If you need to add multiple fields, better use ExpandStruct.

If the field set contains duplicate values, an error is returned.

Arguments:

1. Source structure.
2. Name of the new field.
3. Value of the new field.

Examples

$struct = AsStruct(1 AS a);
SELECT
  AddMember(
    $struct,
    "b",
    2
  ) AS ab;

RemoveMember

Removing a field from the structure.

If the entered field hasn't existed, an error is returned.

Arguments:

1. Source structure.
2. Field name.

Examples

$struct = AsStruct(1 AS a, 2 AS b);
SELECT
  RemoveMember(
    $struct,
    "b"
  ) AS a;

ForceRemoveMember

Removing a field from the structure.

If the entered field hasn't existed, unlike RemoveMember, the error is not returned.

Arguments:

1. Source structure.
2. Field name.

Examples

$struct = AsStruct(1 AS a, 2 AS b);
SELECT
  ForceRemoveMember(
    $struct,
    "c"
  ) AS ab;

CombineMembers

Combining the fields from multiple new structures into another new structure.

If the resulting field set contains duplicate values, an error is returned.

Arguments:

1. Two or more structures.

Examples

$struct1 = AsStruct(1 AS a, 2 AS b);
$struct2 = AsStruct(3 AS c);
SELECT
  CombineMembers(
    $struct1,
    $struct2
  ) AS abc;

FlattenMembers

Combining the fields from multiple new structures into another new structure with prefix support.

If the resulting field set contains duplicate values, an error is returned.

Arguments:

1. Two or more tuples of two elements: prefix and structure.

Examples

$struct1 = AsStruct(1 AS a, 2 AS b);
$struct2 = AsStruct(3 AS c);
SELECT
  FlattenMembers(
    AsTuple("foo", $struct1), -- fooa, foob
    AsTuple("bar", $struct2)  -- barc
  ) AS abc;