Oracle JSON_ARRAYAGG 和 Limit/Rownum
Oracle JSON_ARRAYAGG with Limit/Rownum
我正在使用 Oracle 19c 和 JSON_ARRAYAGG
函数(使用 JSON_OBJECT
)来 return JSON 对象的串联数组字符串。我需要根据 ORDER BY SENT_DATE DESC.
将结果限制为前 10 个对象
请注意,JSON_ARRAYAGG
有自己的 ORDER BY
,所以我把它放在那里。但是,有限制工具吗?
以下语法正确,但结果不正确。我的 JSON 对象在连接字符串中不符合 SENT_DATE DESC 顺序。
SELECT json_arrayagg(json_object('sentDate' value mh.sent_date,
'sentByEmail' value mh.send_by_email,
'sentBy' value mh.sent_by,
'sentByName' value mh.sent_by_name,
'sentToEmail' value mh.sendee_email)
ORDER BY mh.sent_date DESC) /*ORDER BY inside json_arrayagg)*/
/*Normally this works, but not with ROWNUM*/
from mail_history_t mh
where mh.plan_id = 763 and mh.is_current_status = 'Y' and rownum <= 10; /*ROWNUM outside*/
我发现如果我在常用的行查询中检查最前面的结果是不正确的,
select * from mail_history_t where plan_id = 763 and is_current_status ='Y' order by sent_date desc;
您可以先select子查询中的前 10 行,使用 fetch first
行限制子句,然后在外部查询中聚合:
select json_arrayagg(
json_object(
'sentDate' value sent_date,
'sentByEmail' value send_by_email,
'sentBy' value sent_by,
'sentByName' value sent_by_name,
'sentToEmail' value sendee_email
)
order by sent_date desc
) js_array
from (
select *
from mail_history_t
where plan_id = 763 and is_current_status = 'Y'
order by sent_date desc
fetch first 10 rows only
) t
我正在使用 Oracle 19c 和 JSON_ARRAYAGG
函数(使用 JSON_OBJECT
)来 return JSON 对象的串联数组字符串。我需要根据 ORDER BY SENT_DATE DESC.
请注意,JSON_ARRAYAGG
有自己的 ORDER BY
,所以我把它放在那里。但是,有限制工具吗?
以下语法正确,但结果不正确。我的 JSON 对象在连接字符串中不符合 SENT_DATE DESC 顺序。
SELECT json_arrayagg(json_object('sentDate' value mh.sent_date,
'sentByEmail' value mh.send_by_email,
'sentBy' value mh.sent_by,
'sentByName' value mh.sent_by_name,
'sentToEmail' value mh.sendee_email)
ORDER BY mh.sent_date DESC) /*ORDER BY inside json_arrayagg)*/
/*Normally this works, but not with ROWNUM*/
from mail_history_t mh
where mh.plan_id = 763 and mh.is_current_status = 'Y' and rownum <= 10; /*ROWNUM outside*/
我发现如果我在常用的行查询中检查最前面的结果是不正确的,
select * from mail_history_t where plan_id = 763 and is_current_status ='Y' order by sent_date desc;
您可以先select子查询中的前 10 行,使用 fetch first
行限制子句,然后在外部查询中聚合:
select json_arrayagg(
json_object(
'sentDate' value sent_date,
'sentByEmail' value send_by_email,
'sentBy' value sent_by,
'sentByName' value sent_by_name,
'sentToEmail' value sendee_email
)
order by sent_date desc
) js_array
from (
select *
from mail_history_t
where plan_id = 763 and is_current_status = 'Y'
order by sent_date desc
fetch first 10 rows only
) t