Count function with column alias : Count « Aggregate Functions « SQL Server / T-SQL Tutorial






5>
6> create table Billings (
7>     BankerID           INTEGER,
8>     BillingNumber      INTEGER,
9>     BillingDate        datetime,
10>     BillingTotal       INTEGER,
11>     TermsID            INTEGER,
12>     BillingDueDate     datetime ,
13>     PaymentTotal       INTEGER,
14>     CreditTotal        INTEGER
15>
16> );
17> GO
1>
2> INSERT INTO Billings VALUES (1, 1, '2005-01-22', 165, 1,'2005-04-22',123,321);
3> GO

(1 rows affected)
1> INSERT INTO Billings VALUES (2, 2, '2001-02-21', 165, 1,'2002-02-22',123,321);
2> GO

(1 rows affected)
1> INSERT INTO Billings VALUES (3, 3, '2003-05-02', 165, 1,'2005-04-12',123,321);
2> GO

(1 rows affected)
1> INSERT INTO Billings VALUES (4, 4, '1999-03-12', 165, 1,'2005-04-18',123,321);
2> GO

(1 rows affected)
1> INSERT INTO Billings VALUES (5, 5, '2000-04-23', 165, 1,'2005-04-17',123,321);
2> GO

(1 rows affected)
1> INSERT INTO Billings VALUES (6, 6, '2001-06-14', 165, 1,'2005-04-18',123,321);
2> GO

(1 rows affected)
1> INSERT INTO Billings VALUES (7, 7, '2002-07-15', 165, 1,'2005-04-19',123,321);
2> GO

(1 rows affected)
1> INSERT INTO Billings VALUES (8, 8, '2003-08-16', 165, 1,'2005-04-20',123,321);
2> GO

(1 rows affected)
1> INSERT INTO Billings VALUES (9, 9, '2004-09-17', 165, 1,'2005-04-21',123,321);
2> GO

(1 rows affected)
1> INSERT INTO Billings VALUES (0, 0, '2005-10-18', 165, 1,'2005-04-22',123,321);
2> GO

(1 rows affected)
1>
2>
3> SELECT COUNT(*) AS NumberOfBillings,
4>     SUM(BillingTotal - PaymentTotal - CreditTotal) AS TotalDue
5> FROM Billings
6> WHERE BillingTotal - PaymentTotal - CreditTotal > 0
7> GO
NumberOfBillings TotalDue
---------------- -----------
               0        NULL

(1 rows affected)
1>
2> drop table Billings;
3> GO








9.3.Count
9.3.1.COUNT returns the total count of records in a column or the count for DISTINCT (unique) values selected by the query.
9.3.2.COUNT(*) returns the total count of all records (rows) in the column, including NULL values of selected records by the query.
9.3.3.Count function with column alias
9.3.4.Counting unique values.
9.3.5.A common mistake with DISTINCT is to code the DISTINCT statement before the COUNT statement.
9.3.6.Counting values including NULL values.
9.3.7.Using ISNULL to count all values including NULLs.
9.3.8.Count table row in dynamic sql