Question

trying to figure out how to get SQL to read a value as a date.

I have a db that has columns like this:

id  created_at
1   2010-12-16
2   2010-12-16
3   2010-12-17
4   2010-12-21
5   2010-12-23
6   2011-01-04

I did not create the table using SQL; it was generated as text and imported to an SQL server. I’m not sure how to write my query so that it knows that created_at is a date, so I can use clauses like “WHERE created_at <‘2010-10-17’, etc, like I can do from a normal SQL db. Is Cast the route to go here? As in SELECT Cast(created_at as …something?) haven’t been able to find anything useful elsewhere.

Answer 1

if using SQL Server you can cast the column as a date as you’ve guessed:

select cast(created_at as date) 
from myTable

select * 
from myTable 
where cast(created_at as date) >= '2012-01-01'

However you’d need to do that each time you queried the table which is pretty inefficient. Better would be to redefine the table to make that column a date type by default. If you can post your table’s DDL statement (sql to create the table) up here I can write your conversion code for you. Alternatively, use the code below to alter the table after creation:

alter table myTable 
alter column created_at date

Cheers,

JB

Edit based on comments. If you’re unable to change the datatype and it’s an ntext column, first use substring to convert to an nvarchar, then use the cast function:

select * 
from myTable 
where cast(substring(created_at,1,10) as date) >= '2012-01-01'