MySQL 获取这段 { "name": "base.third_code", "value": ["3", "4"] } 中value的每一个元素

要获取MySQL中的JSON字段中的每个元素，可以使用MySQL的JSON来实现。对于给定的JSON字段 { "name": "base.third_code", "value": ["3", "4"] }，可以使用以下SQL查询语句来获取value字段的每个元素：

SELECT JSON_UNQUOTE(JSON_EXTRACT(json_column, '$.value')) AS element1,
JSON_UNQUOTE(JSON_EXTRACT(json_column, '$.value')) AS element2
FROM your_table;

这个查询语句中，json_column是存储JSON数据的列名，your_table是表名。JSON_EXTRACT函数用于提取JSON字段中的指定元素，$表示根节点，value表示value数组的第一个元素，value表示value数组的第二个元素。JSON_UNQUOTE函数用于去除提取出来的元素的引号。

相关问题

优化这段SQL：SELECT CONCAT( HOUR ( mail_send_time ) DIV 1 * 1, ':00-', HOUR ( mail_send_time ) DIV 1 * 1, ':59' ) AS timeInterval, IFNULL( COUNT( * ), 0 ) AS total, IFNULL( SUM( contact_account_type = IF(cv.code_value='01',cv.code_description,'') ), 0 ) AS wxTotal, IFNULL( SUM( contact_account_type = IF(cv.code_value='02',cv.code_description,'') ), 0 ) AS qqTotal, IFNULL( SUM( local_action = IF(cv.code_value='05',cv.code_description,'') AND contact_account_type = IF(cv.code_value='01',cv.code_description,'')), 0 ) AS wxSend, IFNULL( SUM( local_action = IF(cv.code_value='06',cv.code_description,'') AND contact_account_type = IF(cv.code_value='01',cv.code_description,'')), 0 ) AS wxReceive , IFNULL( SUM( local_action = IF(cv.code_value='05',cv.code_description,'') AND contact_account_type = IF(cv.code_value='02',cv.code_description,'')), 0 ) AS qqSend, IFNULL( SUM( local_action = IF(cv.code_value='06',cv.code_description,'') AND contact_account_type = IF(cv.code_value='02',cv.code_description,'')), 0 ) AS qqReceive FROM dwd_t_friend_talk, dwd_t_code_value cv WHERE person_no = '653129200105072624' AND contact_account_type IN ( IF(cv.code_value='01',cv.code_description,''), IF(cv.code_value='02',cv.code_description,'')) AND friend_account <> '' AND contact_account_type <> '' AND mail_send_time IS NOT NULL AND mail_send_time <> '' GROUP BY HOUR ( mail_send_time ) DIV 1

可以考虑以下几种优化方式：

1. 使用JOIN语句代替WHERE语句中的子查询，可以提高查询效率。

2. 对mail_send_time字段创建索引，可以加快查询速度。

3. 可以尝试将COUNT和SUM聚合函数合并成一个SELECT语句，以减少查询次数。

4. 可以考虑将IFNULL函数替换为COALESCE函数，因为COALESCE函数在MySQL中的性能更好。

优化后的SQL如下：

SELECT CONCAT(HOUR(mail_send_time) DIV 1 * 1, ':00-', HOUR(mail_send_time) DIV 1 * 1, ':59') AS timeInterval,
COUNT(*) AS total,
SUM(COALESCE(contact_account_type = IF(cv.code_value='01',cv.code_description,''), 0)) AS wxTotal,
SUM(COALESCE(contact_account_type = IF(cv.code_value='02',cv.code_description,''), 0)) AS qqTotal,
SUM(COALESCE(local_action = IF(cv.code_value='05',cv.code_description,'') AND contact_account_type = IF(cv.code_value='01',cv.code_description,''), 0)) AS wxSend,
SUM(COALESCE(local_action = IF(cv.code_value='06',cv.code_description,'') AND contact_account_type = IF(cv.code_value='01',cv.code_description,''), 0)) AS wxReceive,
SUM(COALESCE(local_action = IF(cv.code_value='05',cv.code_description,'') AND contact_account_type = IF(cv.code_value='02',cv.code_description,''), 0)) AS qqSend,
SUM(COALESCE(local_action = IF(cv.code_value='06',cv.code_description,'') AND contact_account_type = IF(cv.code_value='02',cv.code_description,''), 0)) AS qqReceive
FROM dwd_t_friend_talk
JOIN dwd_t_code_value cv ON contact_account_type IN (cv.code_description)
WHERE person_no = '653129200105072624'
AND friend_account <> ''
AND contact_account_type <> ''
AND mail_send_time IS NOT NULL
AND mail_send_time <> ''
GROUP BY HOUR(mail_send_time) DIV 1;

delimiter // CREATE FUNCTION DBROAM.GET_FORMVALUE ( str in varchar2 ) return number is cursor_name integer; ret integer; val number(12,4); begin val := -1; begin cursor_name := dbms_sql.open_cursor; dbms_sql.parse(cursor_name, 'select '||str||' from dual', dbms_sql.v7); dbms_sql.define_column (cursor_name, 1, val); ret := dbms_sql.execute(cursor_name); if dbms_sql.fetch_rows (cursor_name)<>0 then dbms_sql.column_value (cursor_name, 1, val); end if; dbms_sql.close_cursor(cursor_name); exception when others then dbms_sql.close_cursor(cursor_name); end; return val; end; // delimiter ;改写成mysql可以运行的

好的，根据你提供的Oracle函数代码，我将其转换为MySQL函数代码如下：

delimiter //
CREATE FUNCTION GET_FORMVALUE (str VARCHAR(100)) RETURNS DECIMAL(12,4)
BEGIN
    DECLARE cursor_name INTEGER;
    DECLARE ret INTEGER;
    DECLARE val DECIMAL(12,4);
    
    SET val = -1;
    SET cursor_name = 0;
    SET ret = 0;
    
    BEGIN
        SET cursor_name = (SELECT @@session.pseudo_thread_id);
        PREPARE my_query FROM CONCAT('SELECT ', str, ' FROM dual');
        EXECUTE my_query;
        DEALLOCATE PREPARE my_query;
        
        IF cursor_name > 0 THEN
            SET ret = 1;
        END IF;
        
        IF ret = 1 THEN
            FETCH cursor_name INTO val;
        END IF;
        
        CLOSE cursor_name;
    END;
    
    RETURN val;
END;//
delimiter ;

请注意，MySQL中不存在`dbms_sql`包，所以我使用了动态SQL来编写查询语句。此外，由于MySQL不支持`%TYPE`语法，因此我将返回值类型设置为DECIMAL(12,4)。如果你需要返回不同的数据类型，可以根据需要进行更改。