Question

我创建了自定义类型

 CREATE TYPE address AS (city VARCHAR(90), street VARCHAR(90));

我需要将此类型转换为字符varying[]。我收到错误

无法将customtype_address类型转换为字符变化[]

Answer 1

您需要创建强制转换功能：

[local] @ test #= CREATE TYPE address AS (city VARCHAR(90), street VARCHAR(90));
CREATE TYPE

[local] @ test #=  -- CREATE the cast function
  CREATE OR REPLACE FUNCTION address2varchar_array (address address)
  RETURNS VARCHAR[] AS $$
    SELECT ARRAY[address.city, address.street]
  $$ LANGUAGE SQL;

[local] @ test #= -- CREATE the cast
  CREATE CAST (address AS VARCHAR[]) WITH FUNCTION address2varchar_array(address);

然后：

[local] @ test #= CREATE TEMP TABLE t (a address);
CREATE TABLE

[local] @ test #= INSERT INTO t VALUES (('paris', 'something'));
INSERT 0 1

[local] @ test #= SELECT a::VARCHAR[] FROM t;
┌───────────────────┐
│         a         │
├───────────────────┤
│ {paris,something} │
└───────────────────┘
(1 row)

Answer 2

 CREATE TYPE address AS (city VARCHAR(90), street VARCHAR(90));
 CREATE  TABLE contact1 (adr address);
 INSERT INTO contact1 VALUES (('cityone', 'addressone'));

创建一个如下所示的函数，将address类型转换为varchar[]

create or replace function addresstovarchar(val address) returns 
varchar[] as
$$
select string_to_array(trim(trim(val::text,'('),')'),',')::varchar[] 
$$language sql

用法：

select addresstovarchar(adr) from contact1

在postgresql中将自定义数组类型转换为字符变化数组

2 个答案: