Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Appendix A: System Functions
CHECKSUM_AGG
Like CHECKSUM, this is a basic hash algorithm usually used to detect changes or consistency in data. The
primary difference is that CHECKSUM is oriented around rows, whereas CHECKSUM_AGG is oriented
around columns. The basic syntax is:
CHECKSUM_AGG( [ALL | DISTINCT] )
The expression value can be virtually anything, including, if you wish, concatenation of columns (just
remember to cast as necessary); however, remember that expression order does matter, so if you’re concatenating,
Col1 + Col2 does not equal Col2 + Col1.
COUNT
COUNT returns the number of items in expression. The data type returned is of type int. The syntax is
as follows:
COUNT
(
[ALL | DISTINCT] | *
)
The expression cannot be of the uniqueidentifier, text, image, or ntext data types. The * argument
returns the number of rows in the table; it does not eliminate duplicate or NULL values.
This function supports the OVER operator described in the ranking functions section of this appendix.
COUNT_BIG
COUNT_BIG returns the number of items in a group. This is very similar to the COUNT function just
described, with the exception that the return value has a data type of bigint. The syntax is as follows:
COUNT_BIG
(
[ALL | DISTINCT ] | *
)
Like COUNT, this function supports the OVER operator described in the ranking functions section of this
appendix.
GROUPING
592
GROUPING adds an extra column to the output of a SELECT statement. The GROUPING function is used
in conjunction with CUBE or ROLLUP to distinguish between normal NULL values and those added as a
result of CUBE and ROLLUP operations. Its syntax is:
GROUPING ()