根据时间戳派生新列

Question

我有一个数据类型为文本的列 'customer_date'。

根据我需要导出新列的时间

条件：

when customer_date <12 then 'AM' else 'PM

customer_date

01Mar2018 10:03:54
02Mar2018 13:03:54

预期输出

  customer_date             session

01Mar2018 10:03:54        AM
02Mar2018 13:03:54        PM

当我写

时它抛出错误

select 
case EXTRACT(HOUR FROM customer_date)<12 then 'AM' else 'PM' end as session
from my table;

Answer 1

这在我测试时有效：

select (case when EXTRACT(HOUR FROM customer_date::timestamp) < 12 then 'AM' else 'PM' end) as session
from mytable;

我添加了显式转换和 when。

Answer 2

您忘记在 CASE WHEN 中添加 WHEN，正如@Gordon Linoff 所说。

有一个简单的方法，使用TO_CHAR代替CASE WHEN。

用于TO_CHAR

AM, am, PM or pm will get meridiem indicator (without periods)

CREATE TABLE myTable(customer_Date timestamp);

insert into myTable values ('01Mar2018 10:03:54'::timestamp);

insert into myTable values ('02Mar2018 13:03:54'::timestamp);

查询 1:

select customer_Date,TO_CHAR(customer_Date::timestamp, 'AM') as session
from mytable

Results:

|        customer_date | session |
|----------------------|---------|
| 2018-03-01T10:03:54Z |      AM |
| 2018-03-02T13:03:54Z |      PM |

根据时间戳派生新列

Derive a new column based on Time stamp

sql

postgresql

sql-date-functions

sqldatetime