1.根据出生日期计算当前已满周岁
DECLARE @birth datetime SET @birth='1990-01-01' SELECT (cast(convert(char( 8 ),GETDATE(),112) as int) - cast(convert(char(8),@birth,112) as int))/10000
2.COUNT(expression) just returns the total number of rows in which that expression is not null.
COUNT函数返回值不为null的行数。
| ID | FullName |
| 1 | NULL |
| 2 | NULL |
SELECT COUNT(1) FROM t1 -- Returns 2
SELECT COUNT(FullName) FROM t1 -- Returns 0
COUNT(expression) just returns the total number of rows in which that expression is not null. - See more at: http://www.sqlteam.com/article/how-to-use-group-by-in-sql-server#sthash.b6O058Mg.dpuf
(持续更新中)