Alias exists to name the data generated during the execution of UQL, so that the data can be called subsequently.

Custom Alias

A custom alias is defined using keyword as as soon as the data is generated. A data can be re-defined with different aliases, but only the last defined alias is valid. An alias can only be defined once, even though its data could be re-defined with another alias later, this alias will be considered obsolete and cannot be used for defining other data.

Naming Conventions

Avoid using property names as alias (and use system alias this to disambiguate when necessary), must be using:

• 1 ~ 64 characters
• Not allow to start with wave line '~'
• Not allow to contain back quote '`'
• Not allow to use system reserved words
• (When containing characters other than letters, numbers and underscore, the alias name should be wrapped with backquote '`' when being used in the UQL)

Examples of Defining Alias

When aliases contain only letters, numbers and underscore:

When aliases contain special characters:

with [1,2,3] as `my-list`
return `my-list`

Omission of defining alias for a newly generated data, or defining an alias that is never called, both could induce negative effect on the validity of UQL.

System Alias

this

In practical this is rarely used unless to eliminate any ambiguity. Ambiguity occurs when calling a property whose name corresponds with an active custom alias, in which case this has to be used to refer to the property of node/edge.

The node filter {this.balance > 5000} in below code describes 'the balance of current node should be greater than 5,000':

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

Since node property balance corresponds with alias balance defined in the first statement, omitting this from the filter, which becomes {balance > 5000} such that the description turns into 'alias balance should be greater than 5,000', obviously is not a reasonable filtering condition.

prev_n

prev_n only appears in templates.

• For single node/edge template:

• For multi-edge template:

For the initial-node of a path, whose prev_n does not exist, the judgements of ==, !=, >, >=, <, <= involving its prev_n will return true by default, while the judgements of other operators are unpredictable.

prev_e

prev_e only appears in templates.

• For single node/edge template:

• For multi-edge template:

For the initial-node and the first edge of a path, whose prev_e does not exist, the judgements of ==, !=, >, >=, <, <= involving their prev_e will return true by default, while the judgements of other operators are unpredictable.

Call an Alias

Suppose that nodes, edges, paths, mylist, mypoint, myobject and myitem are aliases of type NODE, EDGE, PATH, list, point, object and others, below call formats are supported:

Type TABLE is not supported to be called in UQL. Regarding how to specify a valid return format in RETURN clause, please read the table at the end of documentation RETURN.