红移时间数据类型

Posted 2023-05-08

【中文标题】红移时间数据类型

【英文标题】：Redshift Time Datatype

【发布时间】：2020-08-31 08:47:53

【问题描述】：

我正在尝试创建和加载与其他数据库不同的 TIME 列来存储，只是时间。即 09:30:00、14:23:16 根据这个https://docs.aws.amazon.com/redshift/latest/dg/r_Datetime_types.html Redshift 有一个 TIME 数据类型。 然而，尝试像日期和时间戳数据类型一样使用它被证明具有挑战性。

select version();
                                                          version                                                          
---------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 8.0.2 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3), Redshift 1.0.18228
(1 row)

-- TimeStamps ------------------------------------------------------------------------
drop table if exists t1;
psql:redshiftTime.sql:4: INFO:  Table "t1" does not exist and will be skipped
DROP TABLE
create table t1 (c1 timestamp);
CREATE TABLE
insert into t1 (select current_timestamp);
INSERT 0 1
insert into t1 values ('2020-03-01 07:30:57.123456');
INSERT 0 1
insert into t1 values ('2020-03-01 07:30:57');
INSERT 0 1

-- Dates -----------------------------------------------------------------------------
drop table if exists t1;
DROP TABLE
create table t1 (c1 date);
CREATE TABLE
insert into t1 (select current_date);
INSERT 0 1
insert into t1 values ('2020-03-01');
INSERT 0 1


-- Times -----------------------------------------------------------------------------
drop table if exists t1;
DROP TABLE
create table t1 (c1 time);   -- FAILS????
psql:redshiftTime.sql:19: ERROR:  Column "t1.c1" has unsupported type "time without time zone".
insert into t1 (select current_time);  
psql:redshiftTime.sql:20: ERROR:  relation "t1" does not exist
insert into t1 values ('12:00:00'); 
psql:redshiftTime.sql:21: ERROR:  relation "t1" does not exist
-- CHAR Woraround ???? ----------------------------------------------------------------
drop table if exists t1;
psql:redshiftTime.sql:25: INFO:  Table "t1" does not exist and will be skipped
DROP TABLE
create table t1 (c1 CHAR(8));
CREATE TABLE
insert into t1 (select current_time);   -- FAILS  - expected due to mismatch data type
psql:redshiftTime.sql:27: INFO:  Function "text(time with time zone)" not supported.
psql:redshiftTime.sql:27: INFO:  Function "timetz(time with time zone,integer)" not supported.
psql:redshiftTime.sql:27: ERROR:  Specified types or functions (one per INFO message) not supported on Redshift tables.
insert into t1 values ('12:00:00'); -- OK
INSERT 0 1
SELECT CAST( current_time AS CHAR(8)); -- OK - automagic substring
  bpchar  
----------
 08:42:24
(1 row)

insert into t1 (SELECT CAST( current_time AS CHAR(8))); -- FAILS
psql:redshiftTime.sql:31: INFO:  Function "text(time with time zone)" not supported.
psql:redshiftTime.sql:31: INFO:  Function "timetz(time with time zone,integer)" not supported.
psql:redshiftTime.sql:31: ERROR:  Specified types or functions (one per INFO message) not supported on Redshift tables.
SELECT CAST( current_time AS CHAR(18)); -- OK 
       bpchar       
--------------------
 08:42:25.411191+00
(1 row)

insert into t1 (SELECT substr(CAST( current_time AS CHAR(18)),1,8)); -- FAILS
psql:redshiftTime.sql:34: INFO:  Function "text(time with time zone)" not supported.
psql:redshiftTime.sql:34: INFO:  Function "timetz(time with time zone,integer)" not supported.
psql:redshiftTime.sql:34: ERROR:  Specified types or functions (one per INFO message) not supported on Redshift tables.

【参考方案1】：

我的测试与您的发现相符。

但是，虽然我无法创建 TIME 类型的列，但我可以转换为 TIME：

SELECT NOW()::TIME

09:10:08

但是，我无法将 TIMESTAMP 表列转换为 TIME。最奇怪的！