如何在 SQL 中将文本列转换为日期列？

Question

I was given a date column in the form of 'YYYY-MM-dd HH:mm:ss UTC'. I have tried using cast and convert to date, datetime, and timestamp, but they all only return the YYYY. Is there any way to return the date correctly from this type of string? I also would like this NewDate column to be added to my table for future use.

Below is the code I have tried

select OrigDate, cast(OrigDate as timestamp) as NewDate from MyTable

Answer 1

SQLite has no special datatype for dates, which can be stored as text or numbers (julian days or epoch timestamp); instead, it has a set of date and time functions that operate on these values.

SQLite recognizes 'YYYY-MM-DD HH:MM:SS' as a valid date format, so to make your strings valid SQLite date formats, you just need to remove the trailing " UTC":

select OrigDate, substring(OrigDate, -4) NewDate  from mytable

Answer 2

You can add the new column with name NewDate to the table like this:

alter table MyTable add NewDate text;

As you can see the data type defined is text because there is no date or datetime data type in SQLite.
Then you can populate/update this column with the local time that each of your UTC datetimes already have in the column OrigDate with the use of the function datetime() :

update MyTable
set NewDate = datetime(substr(OrigDate, 1, 19), 'localtime');

See a simplified demo .