Question

I´m writing an application that relies on Ajax requests to retrieve data from a dataBase, the required info is delivered in a Json set of objects, this means that even for the empty fields of the dataBase a pair of propriety/value is generated:

[{"field1":"value1","field2":"value2","field3":""},{"field1":"","field2":"","field3":""}]

How can I Select only not empty fields from the dataBase via SQL avoiding generating and sending unnecessary data?

Answer 1

If your data in the table is NULL then you can selected records as appropriate using something like

SELECT [fieldList]
  FROM [tableName]
 WHERE [field_1] IS NOT NULL
    OR [field_2] IS NOT NULL
    OR [field_3] IS NOT NULL

However – if you want to omit the definitions from the JSON for partially empty records, such that

{"field1":"value1","field2":"value2","field3":""}

was transmitted as

{"field1":"value1","field2":"value2"}

Then that is something you would need to do by customising whatever JSON Serializer you are using.