PostgreSQL跨3个联接计算百分比

我正在计算一个百分比值来表示进度。我将来自同一列（但值不同）上3个独立计数的数据合并在一起。我是如此接近，但它一直给我零

SELECT a.count1 / (a.count1 + b.count2 + c.count3) FROM
(SELECT count(*) AS "count1"
FROM "stitch_jira"."issues"
WHERE "stitch_jira"."issues"."fields__status__statusCategory__name" = 'To Do') a
CROSS JOIN 
(SELECT count(*) AS "count2"
FROM "stitch_jira"."issues"
WHERE ("stitch_jira"."issues"."fields__status__statusCategory__name" = 'In Progress')) b  
CROSS JOIN 
(SELECT count(*) AS "count3"
FROM "stitch_jira"."issues"
WHERE ("stitch_jira"."issues"."fields__status__statusCategory__name" = 'Done')) c

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关于我为什么在这里得到零结果有什么建议吗？它应该产生“0.4…”

您可以使用条件聚合重写整个查询，并转换为十进制/乘以1.0：

SELECT 
 1.0*(COUNT(*) FILTER(WHERE fields__status__statusCategory__name='To Do'))/
 (COUNT(*) FILTER(WHERE fields__status__statusCategory__name 
                   IN('To Do','In Progress','Done')))
FROM "stitch_jira"."issues"