Extract data from json inside mysql field

Question

I\'ve got a a table with rows, and one of the rows has a field with data like this

{\"name\":\"Richard\",\"lastname\":null,\"city\":\"Olavarria\",\"cityId\":         


        

Answer 1

I have wrapped this into a stored function for those constrained to MySQL <5.7.7:

CREATE FUNCTION `json_extract_string`(
    p_json text,
    p_key text
) RETURNS varchar(40) CHARSET latin1
BEGIN
    SET @pattern = CONCAT('"', p_key, '":"');
    SET @start_i = LOCATE(@pattern, p_json) + CHAR_LENGTH(@pattern);
    if @start_i = CHAR_LENGTH(@pattern) then
        SET @end_i = 0;
    else
        SET @end_i = LOCATE('"', p_json, @start_i) - @start_i;
    end if;
    RETURN SUBSTR(p_json, @start_i, @end_i);
END

Note this only works with string values but is a bit more robust than @DmitryK's answer, in that it returns an empty string if the key is not found and the key can be anywhere in the JSON string.