How to get values from MySQL(5.6) column if that contains json document as string

Question

How to get values from MySQL(5.6) column if that contains JSON document as a string

For example, if we have a table - employee in that we have three columns id, nam

Answer 1

Function above not work properly if you have nested JSON in table field.

Because i needed a JSON_EXTRACT on mysql 5.6 i wrote it by myself a copy of original function that can extract values like the native function in mysql 5.7

Usage:

SELECT JSON_EXTRACT_NESTED(table_field,"json_level1.json_level2.json_level3") FROM table;

If you have one level JSON then you use:

SELECT JSON_EXTRACT_NESTED(table_field,"json_level1") FROM table;

In database you have to add two functions:

Main function:

CREATE FUNCTION `json_extract_nested`(
_field TEXT,
_variable TEXT
) RETURNS TEXT CHARSET latin1
BEGIN
                DECLARE X INT DEFAULT 0;
                DECLARE fieldval1 TEXT;
                DECLARE arrayName,arrayValue TEXT;

                SET arrayName = SUBSTRING_INDEX(_variable, '.', 1);

                IF(LOCATE('%',arrayName)> 0) THEN 
                    SET _field = SUBSTRING_INDEX(_field, "{", -1);
                    SET _field = SUBSTRING_INDEX(_field, "}", 1);
                    RETURN TRIM(
                    BOTH '"' FROM SUBSTRING_INDEX(
                        SUBSTRING_INDEX(
                        SUBSTRING_INDEX(
                            _field,
                            CONCAT(
                            '"',
                            SUBSTRING_INDEX(_variable,'$.', - 1),
                            '":'
                            ),
                            - 1
                        ),
                        ',"',
                        1
                        ),
                        ':',
                        -1
                    )
                    ) ;
                ELSE  
                    SET arrayValue = json_array_value(_field, arrayName);
                    WHILE X < (LENGTH(_variable) - LENGTH(REPLACE(_variable, '.', ""))) DO
                        IF(LENGTH(_variable) - LENGTH(REPLACE(_variable, '.', ""))>X) THEN
                            SET arrayName = SUBSTRING_INDEX(SUBSTRING_INDEX(_variable, '.', X+2),'.',-1);
                        END IF;
                        IF(arrayName<>'') THEN
                            SET arrayValue = json_array_value(arrayValue, arrayName);
                        END IF;
                        SET X = X + 1;
                    END WHILE;
                END IF;
                RETURN arrayValue;
                END$$
DELIMITER ;

Auxiliary function (needed by main function):

CREATE FUNCTION `json_array_value`(
  _field  TEXT,
  arrayName VARCHAR (255)
) RETURNS TEXT CHARSET latin1
BEGIN
                DECLARE arrayValue, arrayValueTillDelimit TEXT;
                DECLARE arrayStartDelimiter, arrayEndDelimiter VARCHAR(10);
                DECLARE arrayCountDelimiter INT;
                DECLARE countBracketLeft, countBracketRight INT DEFAULT 0;
                DECLARE X INT DEFAULT 0;
                DECLARE arrayNameQuoted VARCHAR(255);
                SET arrayNameQuoted = CONCAT('"',arrayName,'"');
                /*check arrayname exist*/
                IF(LOCATE(arrayNameQuoted,_field)= 0) THEN 
                    RETURN NULL;    
                ELSE
                    /*get value behind arrayName1*/
                    SET _field = SUBSTRING(_field,1,LENGTH(_field)-1);
                    SET arrayValue = SUBSTRING(_field, LOCATE(arrayNameQuoted,_field)+LENGTH(arrayNameQuoted)+1, LENGTH(_field));
                    /*get json delimiter*/
                    SET arrayStartDelimiter = LEFT(arrayValue, 1);
                    IF(arrayStartDelimiter='{') THEN
                        SET arrayEndDelimiter = '}';                            
                        loopBrackets: WHILE X < (LENGTH(arrayValue)) DO                 
                            SET countBracketLeft = countBracketLeft +IF(SUBSTRING(arrayValue,X,1)=arrayStartDelimiter,1,0);
                        SET countBracketRight = countBracketRight +IF(SUBSTRING(arrayValue,X,1)=arrayEndDelimiter,1,0);
                        IF(countBracketLeft<>0 AND countBracketLeft=countBracketRight) THEN
                            SET arrayCountDelimiter = X;
                            LEAVE loopBrackets;
                        ELSE
                            SET X = X + 1;
                        END IF;
                        END WHILE;
                                ELSEIF(arrayStartDelimiter='[') THEN
                                    SET arrayEndDelimiter = ']';
                                    SET arrayCountDelimiter = LENGTH(SUBSTRING_INDEX(arrayValue, arrayEndDelimiter, 0));
                                 ELSEIF(arrayStartDelimiter='"') THEN
                                    SET arrayEndDelimiter = '"';
                                    SET arrayCountDelimiter = LENGTH(SUBSTRING_INDEX(arrayValue, arrayEndDelimiter, 0));
                                ELSE 
                                    SET arrayStartDelimiter = "";
                                    IF((LOCATE(",",arrayValue)> LOCATE("}",arrayValue))) THEN
                        SET arrayEndDelimiter = ",";
                        ELSE
                        SET arrayEndDelimiter = "}";
                        END IF;
                        SET arrayCountDelimiter = LENGTH(SUBSTRING_INDEX(arrayValue, arrayEndDelimiter, 0));
                    END IF;
                    SET arrayValueTillDelimit = SUBSTRING(arrayValue, 1, arrayCountDelimiter);
                    SET arrayCountDelimiter = LENGTH(arrayValueTillDelimit) - LENGTH(REPLACE(arrayValueTillDelimit, arrayStartDelimiter, ""));
                    SET arrayValue = SUBSTR(arrayValue,LENGTH(arrayStartDelimiter)+1);
                    IF(arrayStartDelimiter='{') THEN
                        SET arrayValue = SUBSTRING_INDEX(arrayValue, arrayEndDelimiter, arrayCountDelimiter);
                    ELSE
                        SET arrayValue = SUBSTRING_INDEX(arrayValue, arrayEndDelimiter, arrayCountDelimiter+1);
                    END IF;
                    RETURN (arrayValue);
                END IF;
                END$$
DELIMITER ;