An alias is a unique name (identifier) assigned to represent a collection of data of a specific type. Aliases allow users to reference these data throughout the query, enabling data retrieval, manipulation, and further operations.

Declaration and Reference

An alias can be declared using the keyword as immediately after some statements (known as a statement alias) or within a statement method (known as a method alias). The alias represents the data retrieved or generated by the statement.

You can reference an alias later in the query to further utilize the data or return it to the client.

Examples

Refer to the syntax of each statement to determine whether the statement alias and method aliases are supported.

To declare alias e for the find().edges() statement and reference it in the RETURN statement:

find().edges({@direct}) as e
return e.time

The following query throws syntax error because declaring alias for the method edges() is not allowed:

find().edges({@direct} as e)
return e

To declare alias paths for the autonet() statement and alias start for its method src(), then reference them in the RETURN statement:

autonet().src({age < 60} as start).dest({@event}).depth(3) as paths
return start, paths

To declare alias a for the find().nodes() statement, reference it in the WITH statement to compute the minimum age as minAge, reference minAge in another find().nodes() statement to retrieve accounts with that age as alias b, and finally reference b in the RETURN statement to output their names:

find().nodes({@account}) as a
with min(a.age) as minAge
find().nodes({@account.age == minAge}) as b
return b.name

In a path template statement, declare alias start in the first n() and reference it in the last n() to form a simple cycle:

n(as start).e()[3].n({_id == start._id}) as p
return p limit 1

Naming Conventions

Naming conventions for aliases are:

• 1 to 64 characters.
• Cannot start with a tilde (~).
• Cannot contain backquotes (`) or any reserved keywords.

It is suggested not to use a property name for an alias. If necessary, use the system alias this to disambiguate when required.

Alias Type

The alias type matches the data it represents.

In this query, the alias users represents nodes and is of the type NODE, while the alias ages represents the values of the property age, sharing the same type as age:

find().nodes({@user}) as users
return users.age as ages

Referencing an Alias

Depending on the alias type, you can either reference the alias directly in certain statements or extract specific data from the alias for use.

The table below shows examples of alias referencing with different alias types:

More alias referencing formats are supported in the RETURN statement.

System Alias

A system alias are designed for special purposes and can be used without declaration. UQL provides three system aliases: prev_n and prev_e for inter-step filtering in path templates, and this to distinguish a property that shares the same name as an alias when referenced in a filter.

prev_n

The alias prev_n applies exclusively within a node or edge template, referring to the previous node of the current node or edge in a path.

(1) Using prev_n in the single-node template n():

When prev_n is used in the first n() of a path template, there is no preceding node for prev_n to reference. As a result, no results will be returned.

(2) Using prev_n in the single-edge template e():

(3) Using prev_n in the multi-edge template e()[]:

(4) Using prev_n in the multi-edge with intermediates template e().nf()[]:

Note that all nodes referenced by prev_n must have the y property it calls.

This example searches for paths from @actor nodes to @movie nodes, where the rating property of each @movie node must exceed the score property of the preceding @actor node:

n({@actor}).e().n({@movie.rating > prev_n.score}) as p
return p{*}

prev_e

The alias prev_e applies exclusively within a node or edge template, referring to the previous edge of the current node or edge in a path.

(1) Using prev_e in the single-node template n():

When prev_e is used in the first n() of a path template, there is no preceding edge for prev_e to reference. As a result, no results will be returned.

(2) Using prev_e in the single-edge template e():

When prev_e is used in the first e() of a path template, there is no preceding edge for prev_e to reference. As a result, no results will be returned.

(3) Using prev_e in the multi-edge template e()[]:

When prev_e is used in the first e()[] of a path template, the first referenced edge does not exist. As a result, no results will be returned.

(4) Using prev_e in the multi-edge with intermediates template e().nf()[]:

When prev_e is used in the edge template of the first e().nf()[] of a path template, the first referenced edge does not exist. As a result, no results will be returned.

Note that all edges referenced by prev_e must have the y property it calls.

This example searches for 4-step outgoing transaction paths between @card nodes, ensuring ascending transaction times:

n({@card}).re({@transfers}).n({@card})
  .re({@transfers.time > prev_e.time})[3]
  .n({@card}) as p
return p{*}

this

The alias this can be used for disambiguation when an alias referenced in a node or edge filter shares the same name as a node or edge property.

In the following example, the alias balance is declared and balance is also a node property. Using this.balance in the filter specifies that the balance refers to the node property.

... as balance
find().nodes({this.balance > 5000})
...

If {balance > 5000} is used in this case, it refers to the alias balance.

Default Alias

The find().nodes() statement provides a default alias, nodes, to represent the retrieved nodes. Similarly, the find().edges() statement provides a default alias, edges, for the retrieved edges.

You can reference the default alias directly without declaring it.

find().nodes({@account})
return nodes{*}

However, the default alias becomes invalid if a custom alias is declared instead.