Using Internal variables and aliases

Oracle NoSQL Database allows implicit declaration of internal variables. Internal variables are bound to their values during the execution of the expressions that declare them.

The table name in a query may be followed by a table alias. Table aliases are essentially variables ranging over the rows of the specified table. If no alias is specified, one is created internally, using the name of the table as it is spelled in the query.

Example 1: Find the ticket number and passenger details for a given reservation code:

SELECT bagDet.ticketNo, bagDet.fullName, bagDet.contactPhone FROM BaggageInfo bagDet
WHERE confNo="QB1O0J"

Explanation: In this query, you fetch the values of static fields like fullname, ticket number, and contact phone for a particular reservation code. You use a table alias for the BaggageInfo table.

Output:

{"ticketNo":1762390789239,"fullName":"Zina
      Christenson","contactPhone":"987-210-3029"}

If the table alias starts with a dollar sign ($), then it actually serves as a variable declaration for a variable whose name is the alias. This variable is bound to the context row.

Example 2: Fetch the full name and tag number for all customer baggage shipped after 2019.

SELECT fullName, bag.ticketNo FROM BaggageInfo bag WHERE
exists bag.bagInfo[$element.bagArrivalDate >="2019-01-01T00:00:00"]

Explanation: The bag arrival date value for every bag should be greater than the year 2019. Here the "$element" is bound to the context row ( every baggage of the customer). The EXISTS operator checks whether the sequence returned by its input expression is empty or not. The sequence returned by the comparison operator ">=" is non-empty for all bags which arrived after 2019.

Output:

{"fullName":"Lucinda Beckman","ticketNo":1762320569757}
{"fullName":"Adelaide Willard","ticketNo":1762392135540}
{"fullName":"Raymond Griffin","ticketNo":1762399766476}
{"fullName":"Elane Lemons","ticketNo":1762324912391}
{"fullName":"Zina Christenson","ticketNo":1762390789239}
{"fullName":"Zulema Martindale","ticketNo":1762340579411}
{"fullName":"Dierdre Amador","ticketNo":1762376407826}
{"fullName":"Henry Jenkins","ticketNo":176234463813}
{"fullName":"Rosalia Triplett","ticketNo":1762311547917}
{"fullName":"Lorenzo Phil","ticketNo":1762320369957}
{"fullName":"Gerard Greene","ticketNo":1762341772625}
{"fullName":"Adam Phillips","ticketNo":1762344493810}
{"fullName":"Doris Martin","ticketNo":1762355527825}
{"fullName":"Joanne Diaz","ticketNo":1762383911861}
{"fullName":"Omar Harvey","ticketNo":1762348904343}
{"fullName":"Fallon Clements","ticketNo":1762350390409}
{"fullName":"Lisbeth Wampler","ticketNo":1762355854464}
{"fullName":"Teena Colley","ticketNo":1762357254392}
{"fullName":"Michelle Payne","ticketNo":1762330498104}
{"fullName":"Mary Watson","ticketNo":1762340683564}
{"fullName":"Kendal Biddle","ticketNo":1762377974281}