从地图中选择特定值 [英] SELECT Specific Value from map

问题描述

我正在尝试创建一个宽列表，20,000 多列

I am trying to create a WIDE Column Table, 20,000+ columns

最初我想我会使用:

CREATE TABLE details (
   key TEXT,
   detail map<TEXT, TEXT>
   PRIMARY KEY (KEY)
  );

插入此表工作正常

UPDATE details SET detail = detail + { 'col1': '12'} where key='123' ;
UPDATE details SET detail = detail + { 'col20000': 'ABCD'} where key='123' ;

但是，我想阅读一个单独的细节:

However, I would like to read an individual detail:

   select detail[col1] where key='123'

执行此查询时出现以下错误:

when executing this query I get the following error:

 no viable alternative at input '['

这行得通，还是我需要不同的方法?

Will this work, or do I need a different approach?

推荐答案

集合是您一次性获取的一小组数据.

Collections are small groups of data that you fetch all at once.

如果您想在更精细的级别访问元组，并且仍然能够询问给定键的所有数据对是什么"，您应该使用这样的表:

If you want to access tuples at a finer level, and still be able to ask "what are all the pairs of data for a given key," you should use a table like this:

CREATE TABLE details (
  key TEXT,
  detail_key text,
  detail_value text,
  PRIMARY KEY (key, detail_key)
);

这将允许 SELECT * FROM details WHERE key = ? 以及 SELECT * FROM detail WHERE key = ?AND detail_key = ?.

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