我在当前存储为 VARCHAR 的 Postgres 数据库中有一个非常基本的分类列。我可以选择每个计数：
我虽然添加一个ORDER BY array_position()会做到这一点：
SELECT color, count(*)
FROM research
GROUP BY color
ORDER BY array_position(ARRAY['Red','Orange','Yellow','Green','Blue'], color);
但我看到一个类型错误：
ERROR: function array_position(text[], character varying) does not exist
SQL state: 42883
Hint: No function matches the given name and argument types. You might need to add explicit type casts.
Character: 98
我需要投射什么color才能使用该array_position功能对其进行排序？
我有一个级别和年份表，大致如下所示：
INSERT INTO demo(first_name, rank, year) AS VALUES
('Peter',2,2017), ('Robert',3,2016), ('Evelyn',2,2017),
('Rand',3,2017), ('Kofi',3,2017), ('Daniel',3,2016), ('Leonard',1,2017),
('Mary',1,2017), ('Frank',1,2017), ('John',3,2017), ('Mary',1,2016),
('Gilbert',3,2016), ('Quince',2,2017), ('David',3,2017), ('Louis',2,2017),
('Felipe',2,2016), ('Alfonso',1,2017), ('Elise',3,2016), ('Jorge',3,2017),
('Mary',3,2016), ('Jasvant',2,2017), ('Paul',3,2017), ('Richard',2,2017),
('Christopher',2,2017), ('Johannes',2,2016), ('Nasser',3,2016), ('Bruce',3,2017),
('John',3,2016), ('Frederic',3,2016);
我可以用一个非常基本的方法捕获每个级别和年份的总数COUNT()：
SELECT rank, COUNT(*), year
FROM demo
GROUP BY rank, year
ORDER BY year, rank;
这给了我一个相当整洁的演示数据摘要：
Rank Count Year
1 1 2016
2 2 2016
3 8 2016
1 4 2017
2 7 2017
3 7 2017
我的实际数据要大得多，我希望能够在一个看起来更像这样的汇总表中看到它：
Rank 2016 2017 …