SSC-FDM-TD0028

JSON_TABLE not transformed, column names could not be retrieved from semantic information

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This FDM is deprecated, please refer to SSC-EWI-TD0060 documentation.

Description

The JSON_TABLE function can be transformed by SnowConvert, however, this transformation requires knowing the name of the columns that are being selected in the JSON_TABLE ON subquery.

This message is generated to warn the user that the column names were not explicitly put in the subquery (for example, a SELECT * was used) and the semantic information of the tables being referenced was not found, meaning the column names could not be extracted.

Example code

Input Code:

CREATE TABLE demo.Train (
    firstCol INT,
    jsonCol JSON(400),
    thirdCol VARCHAR(30)
);

SELECT * FROM JSON_TABLE 
(ON (SELECT T.*
           FROM demo.Train T)
USING rowexpr('$.schools[*]')
               colexpr('[ {"jsonpath" : "$.name",
                           "type" : "CHAR(20)"},
                          {"jsonpath" : "$.type",
                           "type" : "VARCHAR(20)"}]')
)
AS JT;

SELECT * FROM JSON_TABLE 
(ON (SELECT T.*
           FROM demo.missingTable T)
USING rowexpr('$.schools[*]')
               colexpr('[ {"jsonpath" : "$.name",
                           "type" : "CHAR(20)"},
                          {"jsonpath" : "$.type",
                           "type" : "VARCHAR(20)"}]')
)
AS JT;

Output Code:

CREATE TABLE demo.Train (
    firstCol INT,
    jsonCol VARIANT,
    thirdCol VARCHAR(30)
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"teradata"}}'
;

SELECT
    * FROM
    (
        SELECT
            firstCol,
            rowexpr.value:name :: CHAR(20) AS Column_0,
            rowexpr.value:type :: VARCHAR(20) AS Column_1,
            thirdCol
        FROM
            demo.Train T,
            TABLE(FLATTEN(INPUT => jsonCol:schools)) rowexpr
    ) JT;

    SELECT
    * FROM
    --** SSC-FDM-TD0028 - JSON_TABLE NOT TRANSFORMED, COLUMN NAMES COULD NOT BE RETRIEVED FROM SEMANTIC INFORMATION **
    JSON_TABLE
   (ON
       !!!RESOLVE EWI!!! /*** SSC-EWI-0108 - THE FOLLOWING SUBQUERY MATCHES AT LEAST ONE OF THE PATTERNS CONSIDERED INVALID AND MAY PRODUCE COMPILATION ERRORS ***/!!! (
        SELECT
            T.*
                  FROM
            demo.missingTable T)
   USING rowexpr('$.schools[*]')
                  colexpr('[ {"jsonpath" : "$.name",
                           "type" : "CHAR(20)"},
                          {"jsonpath" : "$.type",
                           "type" : "VARCHAR(20)"}]')
   )
   AS JT;

Recommendations

• Please check the code provided to SnowConvert is complete, if you did not provide the table definition please re-execute the code with the table definition present.

• If you need more support, you can email us at [email protected]