Let parameters

Let query writer is used for creating intermediate variables in query that, for exapmple, would be too complex or repeating otherwise.

This statement is particularly useful in combination with multi-statement executors - batch and transaction.

letValue(name: string, value: any)

Used to create let query writer with provided name and value.

name

Name should be a string containing only alphanumeric characters.

value

Value of variable could be anything. The final value that would be inserted into query is depending on the type on value as such:

• if a raw query - the raw value;
• if a query writer - the final query execution result;
• if null - the string 'NONE';
• if date - the ISO formatted string;
• otherwise - the JSON value stringified.

Reserved names

You can not define variables with reserved names, but can access them in queries:

Variable name	Value
$auth	Represents the currently authenticated scope user
$token	Represents values held inside the JWT token used for the current session
$Scope	Represents the name of the scope of a currently authenticated scope user
$session	Represents values from the session functions as an object
$before	Represents the value before a mutation on a field
$after	Represents the value after a mutation on a field
$value	Represents the value after a mutation on a field (identical to $after in the case of an event)
$input	Represents the initially inputted value in a field definition, as the value clause could have modified the $value variable
$parent	Represents the parent record in a subquery
$event	Represents the type of table event triggered on an event

Helper functions

param(value: string)

Used to insert variable name into query, which would otherwise require the '$' symbol to prefix the name.

So, param('people') and '$people' are basically the same.

Examples

Those are 2 examples how let parameters can be used to factor up the logic of the query.

1. Using letValue for query writer:

await cirql.transaction({
	query: letValue('orgs', select('name').from('organisation'))
}, {
	query: select()
		.from('$orgs') // Note the '$' marking a variable
		.withAny()
})

2. Using letValue for raw value:

await ciqrl.transaction({
	query: letValue('people', ['Alfred', 'Bob', 'John'])
}, {
	query: select()
		.from('person')
		.with(RecordSchema)
		.where({
			name: inside(param('people'))
		})
})