选择varchar列的最小日期

Question

The date column of my table is VARCHAR not datetime.

Eg

entry
'03/01/2011'
'03/22/2011'
'05/22/2010'

when I do a

SELECT min(entry) FROM table

I will get '03/01/2011' as it is the min in alphabetical order. I want to retrieve '05/22/2010' instead which is the min date. How do I convert the column to datetime and get the min.

Thanks

Answer 1

Assuming all entries are 'castable' as datetime :

SELECT MIN(CAST(entry as datetime))
FROM table

---

Assuming there might be some cases where entry isnt a datetime :

SELECT MIN(CAST(ISNULL(NULLIF(ISDATE([entry]),0),'31/12/9999') as datetime))
FROM table

---

If all records are a date column, as @Steve Wellens recommended, I would change the datetype to a datetime field to save future problems

Answer 2

I would fix your database schema. Change the column type to a datetime. Otherwise you'll have problems forever.

Answer 3

当然，使用CAST或CONVERT使varchar成为date （或datetime ）。

Answer 4

Try CAST ing it.

SELECT min(CAST(entry AS DATETIME)) FROM table

Hope this helps.