SQL Dates, Time and Strings
Here are some code snippets to help you get your head around how dates and times work in SQL.
Returns a date with the specified number added, or subtracted from part of that date
/* One month before the current system date */ select * from customers where dateadd(month, -1, getdate())
Returns the number of days, weeks, months or years between two dates.
/* One month before the current system date */ select datediff(day, purchasedate, getdate()) as timeelapsed from salesrecords
UPPER using TRIM
In this example, TRIM removes any spaces in the string, adds a comma, adds the first name field and converts to upper case. This technique can also be used with LOWER and PROPER depending on the desired result.
select upper(trim(LastName)) + ', ' + FirstName AS Name from customers
LEFT and RIGHT
In this example, LEFT will return the first five characters from the name field
select left(Name, 5) from Customers