Query Variables

In this section we'll learn how to create and use Query Variables

Defining Query Variable#

This time let's start explaining variables in dqlx starting from a plain DQL statement.

var(func: eq(name, $0)) {
    film {
        performance {
            D AS genre
        }
    }
}

then you will write the variable this way

variable := dqlx.Variable(dql.EqFn("name", "test")).
    Edge("film").
    Edge("film->performance", dqlx.Select(`
         D AS genre
    `))

If you want to add a variable on an edge you'll use EdgeAs() function, For example:

A AS var(func: eq(name, $0)) {
    B AS film {
        C AS performance {
            D AS genre
        }
    }
}

You'll write

variable := dqlx.Variable(dql.EqFn("name", "test")).
    As("A").
    EdgeAs("B", "film").
    EdgeAs("C", "film->performance", dqlx.Select(`
         D AS genre
    `))

Use the variable#

To use a variable within a query is super simple, just add the variable to a query using the Variable() method then refer to it with the P function (P stands for Predicate).

dqlx
dql

variable := dqlx.Variable(dql.EqFn("name", "test")).
    Edge("film").
    Edge("film->performance", dqlx.Select(`
        D AS genre
    `))

db.QueryType("Film").
    Select("uid").
    Filter(dqlx.Eq{
        "genre": dqlx.P("D"),
    }).
    Variable(variable)

Value Variables#

Value Variables

Value variables store scalar values. Value variables are a map from the UIDs of the enclosing block to the corresponding values.
Value variables are used by extracting the values with val(var-name), or by extracting the UIDs with uid(var-name).

To use value variables you can simply use the Val() function

dqlx
dql

variable := dqlx.Variable(dql.AlloftermsFn("name@en", "The Princess Bride")).
    Edge("starring").
    EdgeAs("pbActors", "starring->performance.actor", dqlx.Select(
        dqlx.As("roles", dqxl.Count("actor.film")),
    ))

db.Query(dqlx.UIDFn(dqlx.P("pbActors"))).
    OrderAsc(dqlx.Val("roles")).
    Select(
        "name@en",
        dqlx.Alias("numRoles", dqlx.Val(roles)),
    )