Aggregate JSON fields in Postgres 9.3

Question

我有一个json列，名为Info，带有以下值：

    {"width":"800, "height":"480"}
    {"width":"800, "height":"480"}
    {"width":"768, "height":"480"}

我需要一个SQL查询才能以这种格式输出：

    Label   |Count
    ==============
    800x480, 2
    768x480, 1

第二个值代表计数。

我设法做的是提取第一值和计数：

    select info->>'width' as label, count(info->>'width') from table_name  GROUP BY 1 ORDER BY 2 DESC LIMIT 5

输出：

    Label   |Count
    ==============
    800, 2
    768, 1

Answer 1

常规字符串串联应该这样做。由于某些原因，如果您从查询中省略了()，则查询会失败。

SELECT (info->>'width') || 'x' || (info->>'width') AS label,
    COUNT(info->>'width')
FROM table_name
GROUP BY 1
ORDER BY 2 DESC
LIMIT 5