The GROUP BY clause can be used in the SELECT statement which invokes the JSON_AGG function. Existing rules for the GROUP BY clause and aggregate functions apply to JSON_AGG. When this is used, the resulting JSON document is structured as an array with objects as its elements that represent members of the resulting group. Each group is in a different output row.
If one of the values used to compose the JSON object is a Vantage NULL, it is returned in the JSON instance as a JSON null.
Rules and Restrictions
- Numeric data types in Vantage map to a number in JSON.
- Nulls in Vantage map to nulls in JSON.
- All other data types in Vantage map to a string in JSON.
You cannot use structured UDTs with LOB attributes as input.
JSON_AGG writes out the values of all attributes of a structured UDT in a comma-separated list enclosed in parenthesis. For example: (att1Val, att2Val, ..., attNVal). If this cannot be done in 64000 bytes, an SQL error is reported and the query fails.
Input character data can contain escape characters that have not been correctly escaped to conform to JSON syntax. When the function encounters these unescaped characters, it will encode the input so that it conforms to proper JSON syntax. However, a syntax error will still be returned if after escaping, the truncated data results in incorrect JSON syntax.
All non-predefined types, such as all UDTs, use their transformed value to populate the resulting JSON document. The user must provide a transform that outputs data in valid JSON syntax in order to function properly. Otherwise, validation of the JSON instance will fail and the function returns an error message. However, as stated above, the function will accept unescaped characters and will not return an error in this case.
The data type in the JSON value is determined according to the mapping above, based on the predefined data type of the result of the transform. All non-LOB predefined types are formatted according to the optional FORMAT clause specified for any particular column, or if that is not present, the default format for the particular data type.
The param name can be specified using the optional "AS" clause for each parameter. If the optional portion is NULL, the names of the parameters that make up the resulting JSON document are given according to current naming conventions of expressions in Vantage.