比较Postgres中两个逗号分隔的列

Question

我有一个Postgres（版本11）表，其中有两个逗号分隔的值，如下所示。 可以进行比较以确定缺少哪个特定值。

Category                                       Comparison category
2219,2220,2991,2992,3577,3617,3624,3884        2992,3617,3884
2145,2150,3594,3597,3600,3626                  2150,3594,3600,3626
2237                                           2237
2991,2992,3884                                 2991,2992,3884
2991,3884                                      2991,3884
2145,2993,3597,3631                            2993,3631
1113,2882,3490,4,4034,922,985                  2882,3490,4,4034,922,985

预期输出：

 Category                             Comparison category   Comments
    2219,2220,2991,2992..             2992,3617,3884       2219,2220,..not in category,But all Categories in comparison column is present in Category column. column     
    2145,2150,3594,3597,3600,3626     2150,3594,3600,3626. 2145,3597 not in category column,But all Categories in comparison column is present in Category column.
    2237                              2237                 Matching
    2991,2992,3884                    2991,2992,3884       Matching
    2991,3884                         2991,3884            Matching
    2145,2993,3597,3631               2993,3631            2145,3597 not in Category column,But all Categories in comparison column is present in Category column.

Answer 1

如果您可以安装intarray扩展名，则可以执行以下操作：

select category, comparison_category, 
       string_to_array(category, ',')::int[] - string_to_array(comparison_category, ',')::int[]
from the_table;

如果您无法安装扩展程序，则它会更加复杂：

select category, comparison_category, 
       (select string_agg(c,',')
        from unnest(string_to_array(category, ',')) as x(c)
        where x.c not in (select cc
                          from unnest(string_to_array(comparison_category, ',')) as t(cc))
        )
from the_table;

但是正确的解决方案是修复数据模型。