我有一列包含 JSON 数组,如下所示:
{data=[{"name":"col1","min":0,"max":32,"avg":29},
{"name":"col2","min":1,"max":35,"avg":21},
{"name":"col3","min":4,"max":56,"avg":34}]}
我正在尝试解析数组并根据条件提取特定值。例如"min"
的值哪里"name"="col1"
: 0"avg"
的值哪里"name"="col3"
: 34有没有人有解决方案?
最佳答案
您的 JSON 无效。应该是 {"data":[
不是 {data = [
如果 JSON 有效(您可以在子查询中轻松修复它),提取数据,将其转换为数组(行)并使用 CASE 表达式获取值。我在这里添加了 max() 聚合以删除 NULL 记录并在单行中获取所有必需的值,您可以改用过滤器(例如 where x.name = 'col1'
),具体取决于您的需要:
with mydata as (
select '{"data":[{"name":"col1","min":0,"max":32,"avg":29},
{"name":"col2","min":1,"max":35,"avg":21},
{"name":"col3","min":4,"max":56,"avg":34}]}' json
)
select max(case when x.name = 'col1' then x.min end) min_col1,
max(case when x.name = 'col3' then x.avg end) avg_col3
from mydata
CROSS JOIN
UNNEST(
CAST(
JSON_EXTRACT(json,'$.data')
as ARRAY(ROW(name VARCHAR, min INTEGER, max INTEGER, avg INTEGER))
)
) as x(name, min, max, avg) --column aliases
结果:min_col1 avg_col3
0 34
关于sql - 在 Presto 中从 JSON 数组中提取值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/66015729/