SQL Advanced (7) Date function

SQL Advanced (7) Date function SQL dates when we work on dates, the hardest task is to make sure that the date is inserted in a format that matches the format of the date column in the database.
As long as the data contains only the date parts, running the query will not be a problem. However, if time is involved, the situation is a little more complicated.
Before we discuss the complexity of the date query, let's look at the most important built-in date processing functions.
The table below the SQL Server date function lists the most important built-in date functions in SQL Server:

function	Description
GETDATE ()	Returns the current date and time
DATEPART ()	Returns a separate part of the date/time
DATEADD ()	Add or subtract a specified time interval in a date
DATEDIFF ()	Returns a time between two dates
CONVERT ()	Display Date/time in a different format

SQL Date data type SQL Server uses the following data types to store date or date/time values in the database:

• DATE-Format YYYY-MM-DD
• DATETIME-format: Yyyy-mm-dd HH:MM:SS
• smalldatetime-format: Yyyy-mm-dd HH:MM:SS
• TIMESTAMP-Format: Unique number

SQL Date Processing If the time section is not involved, then we can easily compare two dates!
Suppose we have the following "Orders" table:

OrderId	ProductName	OrderDate
1	Computer	2008-12-26
2	Printer	2008-12-26
3	Electrograph	2008-11-12
4	Telephone	2008-10-19

Now, we want to select a record from the table above that OrderDate is "2008-12-26".
We use the following SELECT statement:

SELECT * from Orders WHERE orderdate= ' 2008-12-26 '

Result set:

OrderId	ProductName	OrderDate
1	Computer	2008-12-26
3	Electrograph	2008-12-26

Now suppose that "Orders" is similar (note the time section in the "OrderDate" column):

OrderId	ProductName	OrderDate
1	Computer	2008-12-26 16:23:55
2	Printer	2008-12-26 10:45:26
3	Electrograph	2008-11-12 14:12:08
4	Telephone	2008-10-19 12:56:10

If we use the SELECT statement above:

SELECT * from Orders WHERE orderdate= ' 2008-12-26 '

Then we won't get the result. This is because the query does not contain a date for the time part.
Tip: If you want to make queries simple and easier to maintain, don't use the time section in dates!

SQL Advanced (7) Date function