不使用 ARRAY[] 的嵌套复合类型数组的语法

Question

CREATE TYPE pencil_count AS(
    pencil_color varchar(30),
    count integer
);

CREATE TYPE pencil_count_with_date(
date_ date,
pencil_count pencil_count[]
);

CREATE TABLE pencils(id serial, pencils_ pencil_count_with_date[]);

INSERT INTO pencils(pencils_) 
VALUES('{"(\"2016-03-13\",{"(\"blue\",1)","(\"red\",2)"})"}');

如果我想在不使用ARRAY[...] 的情况下添加此复合数组，正确的语法是什么？

Answer 1

当您添加新的嵌套级别时，使用文字字符串的可读性会降低：

CREATE TYPE pencil_count AS(pencil_color varchar(30)
       ,"count" int);

CREATE TYPE pencil_count_with_date AS(date_ date
                                     ,pencil_count pencil_count[]);

CREATE TABLE pencils(id serial, pencils_ pencil_count_with_date[]);

INSERT INTO pencils(pencils_) 
VALUES('{"(
               \"2016-03-13\",
               \"{
                   \"\"(Blue,5)\"\",
                   \"\"(Red,2)\"\"
               }\"
          )"}');   


SELECT pencils_[1].pencil_count[1].pencil_color
FROM pencils;

SqlFiddleDemo

备注：

1. 您需要根据嵌套级别使用" 转义\ 引用每个级别。
2. 这种模式看起来像是试图将 OO 世界引入数据库。它可能比标准化版本更难维护和更慢。 Related question.
3. 如果需要，您可以使用 $$ 引用字符串文字。
4. 使用ARRAY 和ROW 可能更容易发现每个关卡的开始和停止位置。

Answer 2

再次询问 Postgres。扩展your previous question的过程：

CREATE TEMP TABLE pencil_count (
  pencil_color varchar(30)
, count integer
);

CREATE TABLE pencil_count_with_date (
 date_ date,
 pencil_count pencil_count[]
);

CREATE TABLE pencils (
  id serial
, pencils_ pencil_count_with_date[]
);

向 Postgres 询问每个嵌套级别：

INSERT INTO pencil_count VALUES ('red' , 1), ('blue', 2);

SELECT ARRAY(SELECT p FROM pencil_count p)::text AS p_row_arr;

-- with result from above:
INSERT INTO pencil_count_with_date(date_, pencil_count)
VALUES ('2016-04-14', '{"(red,1)","(blue,2)"}')
     , ('2016-04-14', '{"(red,3)","(blue,4)"}');

SELECT ARRAY(SELECT p FROM pencil_count_with_date p)::text AS p2_row_arr;

-- with result from above:
INSERT INTO pencils(pencils_)
VALUES
  ('{"(2016-04-14,\"{\"\"(red,1)\"\",\"\"(blue,2)\"\"}\")"
    ,"(2016-04-15,\"{\"\"(red,3)\"\",\"\"(blue,4)\"\"}\")"}');

SELECT id, pencils_::text FROM pencils;

结果：

id | pencils_
---+-------------------------------------------------------
1  | {"(2016-04-14,\"{\"\"(red,1)\"\",\"\"(blue,2)\"\"}\")"
     ,"(2016-04-15,\"{\"\"(red,3)\"\",\"\"(blue,4)\"\"}\")"}

SQL Fiddle.

到目前为止，我完全同意建议：多级嵌套行类型通常是复杂且低效的。考虑标准化。

我对您之前问题的回答中的更多内容：

• Correct syntax for array of composite type