技術標籤：Presto SQLprestojson

Presto如何把Json陣列分解為多行資料

• Cross Join Unnest

Cross Join Unnest

json格式如下：

{
    "attendances":[
        {
            "attendanceToken":"e333e39b-033a-4db3-9c33-ed777b1ea6fb",
            "userMeta":"{}",
            "roleCode"
 
:"participant",
            "enterTime":1604490880630,
            "exitTime":1604492850267,
            "userDevice":"tablet",
            "externalUserId":"41438910",
            "attendanceRefCode":"5496dc8b-05aa-45bd-b3a4-0062a822803c"
 
,
            "displayName":"Lisa Guo"
        },
        {
            "attendanceToken":"a7cdd08c-ab17-47f3-99d6-e175887511aa",
            "userMeta":"{}",
            "roleCode":"host",
            "enterTime"
 
:1604491369673,
            "exitTime":1604491446190,
            "userDevice":"desktop",
            "externalUserId":"44e3bfc0-4924-4404-b77b-f2d066a15ec6",
            "attendanceRefCode":"fef1f257-4cdc-4805-b60b-65147195af2f",
            "displayName":"Joseph V."
        },
        {
            "attendanceToken":"a7cdd08c-ab17-47f3-99d6-e175887511aa",
            "userMeta":"{}",
            "roleCode":"host",
            "enterTime":1604491394440,
            "exitTime":1604492898877,
            "userDevice":"desktop",
            "externalUserId":"44e3bfc0-4924-4404-b77b-f2d066a15ec6",
            "attendanceRefCode":"fef1f257-4cdc-4805-b60b-65147195af2f",
            "displayName":"Joseph V."
        }
    ]
}

程式碼為：

// An highlighted block
select
	name,
	attendance['attendanceToken'] as attedanceToken,
	attendance['userMeta'] as userMeta,
	attendance['roleCode'] as roleCode,
	from_unixtime(cast(attendance['enterTime'] as BIGINT)/1000, 'Asia/Shanghai') as enterTime,
	from_unixtime(cast(attendance['exitTime'] as BIGINT)/1000, 'Asia/Shanghai') as exitTime,
	attendance['userDevice'] as userDevice,
	attendance['externalUserId'] as externalUserId,
	attendance['attendanceRefCode'] as  attendanceRefCode,
	attendance['displayName'] as displayName
from
	(
	select
		r.name,
		cast(json_extract(r.attendance_detail__c,
		'$.attendances') as array<map<VARCHAR,
		VARCHAR>>) attendances
	from
		reservation r)
cross join unnest (attendances) as attendances(attendance)

結果如下：