SQL Working With Dates

SQL Dates

As long as your data contains only the date portion, your queries will work as expected. However, if a time portion is involved, it gets more complicated.

SQL Date Data Types

MySQL

MySQL comes with the following data types for storing a date or a date/time value in the database:

  • DATE - format YYYY-MM-DD
  • DATETIME - format: YYYY-MM-DD HH:MI:SS
  • TIMESTAMP - format: YYYY-MM-DD HH:MI:SS
  • YEAR - format YYYY or YY

SQL Server

SQL Server comes with the following data types for storing a date or a date/time value in the database:

  • DATE - format YYYY-MM-DD
  • DATETIME - format: YYYY-MM-DD HH:MI:SS
  • SMALLDATETIME - format: YYYY-MM-DD HH:MI:SS
  • TIMESTAMP - format: a unique number

SQL Working with Dates

Look at the following table:

Orders Table

OrderId ProductName OrderDate
1 Geitost 2008-11-11
2 Camembert Pierrot 2008-11-09
3 Mozzarella di Giovanni 2008-11-11
4 Mascarpone Fabioli 2008-10-29

Now we want to select the records with an OrderDate of “2008-11-11” from the table above.

We use the following SELECT statement:

SQL 
 SELECT * FROM Orders WHERE OrderDate='2008-11-11'

The result-set will look like this:

OrderId ProductName OrderDate
1 Geitost 2008-11-11
3 Mozzarella di Giovanni 2008-11-11

Now, assume that the “Orders” table looks like this (notice the added time-component in the “OrderDate” column):

OrderId ProductName OrderDate
1 Geitost 2008-11-11 13:23:44
2 Camembert Pierrot 2008-11-09 15:45:21
3 Mozzarella di Giovanni 2008-11-11 11:12:01
4 Mascarpone Fabioli 2008-10-29 14:56:59

If we use the same SELECT statement as above:

SQL 
 SELECT * FROM Orders WHERE OrderDate='2008-11-11'

we will get no result! This is because the query is looking only for dates with no time portion.