CREATE DEFINER=`your_dbname`@`%` FUNCTION `fn_Json_getKeyValue`(`in_JsonArray` VARCHAR(4096),`in_Index` tinyint,`in_KeyName` VARCHAR(64)) RETURNS varchar(512) CHARSET utf8
BEGIN
DECLARE vs_return VARCHAR(4096);
DECLARE vs_JsonArray, vs_Json, vs_KeyName VARCHAR(4096);
#declare vs_Json varchar(4096);
DECLARE vi_pos1, vi_pos2 SMALLINT UNSIGNED;
#获取json字段 key值
SET vs_JsonArray = TRIM(in_JsonArray);
SET vs_KeyName = TRIM(in_KeyName);
IF vs_JsonArray = '' OR vs_JsonArray IS NULL
OR vs_KeyName = '' OR vs_KeyName IS NULL
OR in_Index <= 0 OR in_Index IS NULL THEN
SET vs_return = NULL;
ELSE
#去掉方括号
SET vs_JsonArray = REPLACE(REPLACE(vs_JsonArray, '[', ''), ']', '');
#取指定的JSON对象
SET vs_json = SUBSTRING_INDEX(SUBSTRING_INDEX(vs_JsonArray,'}', in_index),'}',-1);
IF vs_json = '' OR vs_json IS NULL THEN
SET vs_return = NULL;
ELSE
SET vs_KeyName = CONCAT('"', vs_KeyName, '":');
SET vi_pos1 = INSTR(vs_json, vs_KeyName);
IF vi_pos1 > 0 THEN
#如果键名存在
SET vi_pos1 = vi_pos1 + CHAR_LENGTH(vs_KeyName);
SET vi_pos2 = LOCATE(',', vs_json, vi_pos1);
IF vi_pos2 = 0 THEN
#最后一个元素没有','分隔符,也没有结束符'}'
SET vi_pos2 = CHAR_LENGTH(vs_json) + 1;
END IF;
SET vs_return = REPLACE(MID(vs_json, vi_pos1, vi_pos2 - vi_pos1), '"', '');
END IF;
END IF;
END IF;
RETURN(vs_return);
END