# Introduction # PRAGMA settings # Transactions # Indexes # Optimizing queries # Moving code into SQL # User functions # Callback functions # Reducing database file size # Reducing database load time # Reducing SQL query parse time # Hacking the source # Using the btree interface # Multiple threads # Operating system issues

More on DATEs and SQL Building on this First/Last day of month post (oddly, one of the main ways people seem to land on my blog), here are some other commonly needed SQL queries: Beginning of period Midnight of any day (i.e. truncate the time from a date) SELECT DATEADD(dd, DATEDIFF(dd, 0, TheDate), 0) This works by subtracting the supplied date (like GetDate() for today) from zero--which Microsoft SQL Server interprets as 1900-01-01 00:00:00 and gives the number of days. This value is then re-added to the zero date yielding the same date with the time truncated.

When you follow online communities dedicated to SQL Server with open eyes, you certainly notice a whole lot of questions are closely related to the DATETIME datatype in one way or the other. Obviously, working with DATETIME not as easy as it may seem. To me this seems kind of strange. My believe is that working with DATETIME is actually easy. There is nothing magic about the datatype itself. And there is no magical or esoterical date calculus involved when doing date arithmetic. One only needs to understand some basic concepts of how the DATETIME datatype works in order to deal safely with temporal data. The purpose of this article is to help the reader gain an understanding of this interesting part of SQL Server, and to set some facts clear about this datatype.