如何使用JSONB值的日期/时间函数？

Question

我通常使用这种语法按天分组：

SELECT date_trunc('day', loggedin) AS "Day" , count(*) AS "No. of users"
FROM logins
WHERE created > now() - interval '3 months' 
GROUP BY 1 
ORDER BY 1;

现在我的Date-value位于名为extras的JSONB列中。

SELECT date_trunc('day', "extras"->>'sent') AS date , count(*) AS "value"
FROM "document"
GROUP BY 1 
ORDER BY 1;

这会出现此错误：

  

错误：函数date_trunc（unknown，text）不存在第1行：   选择date_trunc（＆＃39; day＆＃39;，＆＃34; extras＆＃34; - ＆gt;＆gt;＆＃39;发送＆＃39;）AS日期，计数（...                  ^提示：没有函数匹配给定的名称和参数类型。您可能需要添加显式类型转换。

有没有办法让这项工作？

Answer 1

将extras->>'sent'的文字投放到date：

SELECT date_trunc('day', ("extras"->>'sent')::date) AS date , count(*) AS "value"
FROM "document"
GROUP BY 1 
ORDER BY 1;