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    AnalyticDB:JSON

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    AnalyticDB:JSON

    Last Updated:Jul 05, 2024

    AnalyticDB for MySQL supports the JSON data type. This topic describes the format, usage notes, and examples of the JSON data type.

    Usage notes

    • AnalyticDB for MySQL supports the standard JSON format. When you write JSON strings to a table, you must comply with the standard JSON format.

    • Default values cannot be set for columns of the JSON data type.

    JSON format requirements

    When you use JSON data in AnalyticDB for MySQL, take note of the following requirements on keys and values:

    • Keys

      You must enclose a key in double quotation marks (""). Example: "addr" in {"addr":"xyz"}.

    • Values

      • The following data types are supported for a value: BOOLEAN, NUMBER, VARCHAR, ARRAY, OBJECT, and NULL.

        Note

        • A value of the NUMBER type in a JSON index must be within the allowed value range of the DOUBLE type.

        • AnalyticDB for MySQL allows you to write JSON arrays, including plain arrays and nested arrays. Examples: {"hobby":["basketball", "football"]} and {"addr":[{"city":"beijing", "no":0}, {"city":"shenzhen", "no":0}]}.

      • If a value is of the STRING type, you must enclose the value in double quotation marks ("").

        Note

        If a value is of the STRING type and contains double quotation marks (""), you must add escape characters before the double quotation marks to indicate that the double quotation marks are part of the value. For example, the value in {"addr":"xyz"ab"c"} is "xyz"ab"c". The value must be escaped as "xyz\"ab\"c". Backslashes (\) are escaped when data is written. In this case, you must write {"addr":"xyz\\"ab\\"c"}.

      • If a value is of the NUMBER type, you can directly write the value to the table instead of enclosing the value in double quotation marks ("").

      • If a value is of the BOOLEAN type, you must write true or false instead of 1 or 0 to the table. true and false must be in lowercase.

      • If a value is NULL, you must write Null to the table.

      • A key can have values of different data types. The value of the data type that you specified is returned during queries.

        For example, if the INSERT INTO test_tb1 VALUES ({"id":1}) statement is executed, the value of id is 1. If the INSERT INTO test_tb1 VALUES ({"id":"1"}) statement is executed, the value of id is "1".

        If the SELECT id FROM test_tb1 WHERE json_extract(col, '$.id')= 1; statement is executed, "id": 1 is returned. If the SELECT id FROM test_tb1 WHERE json_extract(col, '$.id')= '1'; statement is executed, "id": "1" is returned.

    Examples

    Create a table

    CREATE TABLE json_test(
  id int,
  vj json 
)
DISTRIBUTED BY HASH(id);

    Write data

    Fields of the JSON type are written to tables in single quotation marks (''), in the same manner as fields of the VARCHAR type. The following SQL statements provide examples of different JSON formats: 

    INSERT INTO json_test VALUES(0, '{"id":0, "name":"abc", "age":0}');
INSERT INTO json_test VALUES(1, '{"id":1, "name":"abc", "age":10, "gender":"f"}');
INSERT INTO json_test VALUES(2, '{"id":3, "name":"xyz", "age":30, "company":{"name":"alibaba", "place":"hangzhou"}}');
INSERT INTO json_test VALUES(3, '{"id":5, "name":"a\\"b\\"c", "age":50, "company":{"name":"alibaba", "place":"america"}}');
INSERT INTO json_test VALUES(4, '{"a":1, "b":"abc-char", "c":true}');
INSERT INTO json_test VALUES(5, '{"uname":{"first":"lily", "last":"chen"}, "addr":[{"city":"beijing", "no":1}, {"city":"shenzhen", "no":0}], "age":10, "male":true, "like":"fish", "hobby":["basketball", "football"]}');

    Query data

    AnalyticDB for MySQL allows you to use the json_extract() function to query data.

    • Syntax

      json_extract(json, jsonpath)

    • Description

      This function extracts one or more values specified by jsonpath from a valid JSON string.

    • Parameters

      • json: the name of the column of the JSON type.

      • jsonpath: the path of the key that is separated by periods (.). $ specifies the outermost path.

      For information about JSON functions, see JSON functions.

    • Examples

      • Basic query

        SELECT json_extract(vj,'$.name') FROM json_test WHERE id=1;

      • Equivalent query

        SELECT id, vj FROM json_test WHERE json_extract(vj, '$.name') = 'abc';
SELECT id, vj FROM json_test WHERE json_extract(vj, '$.c') = true;
SELECT id, vj FROM json_test WHERE json_extract(vj, '$.age') = 30;
SELECT id, vj FROM json_test WHERE json_extract(vj, '$.company.name') = 'alibaba';

      • Range query

        SELECT id, vj FROM json_test WHERE json_extract(vj, '$.age') > 0;
SELECT id, vj FROM json_test WHERE json_extract(vj, '$.age') < 100;
SELECT id, vj FROM json_test WHERE json_extract(vj, '$.name') > 'a' and json_extract(vj, '$.name') < 'z';

      • IS NULL or IS NOT NULL query

        SELECT id, vj FROM json_test WHERE json_extract(vj, '$.remark') is null;
SELECT id, vj FROM json_test WHERE json_extract(vj, '$.name') is not null;

      • IN query

        SELECT id, vj FROM json_test WHERE json_extract(vj, '$.name') in ('abc','xyz');
SELECT id, vj FROM json_test WHERE json_extract(vj, '$.age') in (10,20);

      • LIKE query

        SELECT id, vj FROM json_test WHERE json_extract(vj, '$.name') like 'ab%';
SELECT id, vj FROM json_test WHERE json_extract(vj, '$.name') like '%bc%';
SELECT id, vj FROM json_test WHERE json_extract(vj, '$.name') like '%bc';

      • ARRAY query

        SELECT id, vj FROM json_test WHERE json_extract(vj, '$.addr[0].city') = 'beijing' and json_extract(vj, '$.addr[1].no') = 0;
        Note

        When you query arrays, you can use subscripts of specific data. The subscript value starts from 0. You cannot iterate through an entire array.

    References

    JSON indexes