Mysql中JSON操作函数JSON_EXTRACT()

{
    "num": 123,
    "arr": [1,2],
    "obj": {
        "a": 3,
        "b": 4
    }
}
$.num //结果：123
$.arr //结果：[1, 2]
$.arr[1] //结果：1
$.obj.a //结果：3

select 
    oi.oi_id order_item_id,
    replace(JSON_EXTRACT(o.coupon_json,'$.couponPlatDTO.c_sn'),'"','') coupon_sn
from fx_orders_items oi 
INNER JOIN fx_orders o on oi.o_id = o.o_id 
where  o.o_id = 6947877031523765285;
## replace(str,'"','')  -- 将str中双引号"替换为空

{
    "couponPlatDTO": {
        "c_sn": "HYQD1219100037457642053929",
        "couponBatchId": "cb_130011",
        "couponBatchName": 牌-满99减10元电商券",
        "couponDenominationPrice":"10",
        "couponPlatDiscountPrice":"10.00",
        "useCoupon":1
    }
    "usePlatCoupon":1,
    "useStoreCoupon":0
}