两条经典SQL语句（有关日期查询）_[SQL Server教程]
1.用一条语句得出某日期所在月份的最大天数？ SELECT DAY(DATEADD(dd, -DAY('2004-02-13'), DATEADD(mm, 1, '2004-02-13'))) AS 'Day Number'
2.少记录变成多条记录问题
有表tbl
日期 收入 支出
2004-02-11 00:00:00 60 45
2004-03-01 00:00:00 60 45
2004-03-02 00:00:00 40 50
2004-03-05 00:00:00 50 40
/*
测试数据：
Create Table tbl([日期] smalldatetime,[收入] int ,[支出] int)
Insert Into tbl
SELECT '2004-02-11', 60, 45
union SELECT '2004-03-01',60, 45
union SELECT '2004-03-02',40, 50
union SELECT '2004-03-05',50, 40
*/
要得到的结果：
日期 收入 支出 余额
2004-02-01 00:00:00 NULL NULL NULL
2004-02-02 00:00:00 NULL NULL NULL
2004-02-03 00:00:00 NULL NULL NULL
2004-02-04 00:00:00 NULL NULL NULL
2004-02-05 00:00:00 NULL NULL NULL
2004-02-06 00:00:00 NULL NULL NULL
2004-02-07 00:00:00 NULL NULL NULL
2004-02-08 00:00:00 NULL NULL NULL
2004-02-09 00:00:00 NULL NULL NULL
2004-02-10 00:00:00 NULL NULL NULL
2004-02-11 00:00:00 60 45 15
2004-02-12 00:00:00 NULL NULL 15
2004-02-13 00:00:00 NULL NULL 15
2004-02-14 00:00:00 NULL NULL 15
2004-02-15 00:00:00 NULL NULL 15
2004-02-16 00:00:00 NULL NULL 15
2004-02-17 00:00:00 NULL NULL 15
2004-02-18 00:00:00 NULL NULL 15
2004-02-19 00:00:00 NULL NULL 15
2004-02-20 00:00:00 NULL NULL 15
2004-02-21 00:00:00 NULL NULL 15
2004-02-22 00:00:00 NULL NULL 15
2004-02-23 00:00:00 NULL NULL 15
2004-02-24 00:00:00 NULL NULL 15
2004-02-25 00:00:00 NULL NULL 15
2004-02-26 00:00:00 NULL NULL 15
2004-02-27 00:00:00 NULL NULL 15
2004-02-28 00:00:00 NULL NULL 15
2004-02-29 00:00:00 NULL NULL 15
2004-03-01 00:00:00 60 45 30
2004-03-02 00:00:00 40 50 20
2004-03-03 00:00:00 NULL NULL 20
2004-03-04 00:00:00 NULL NULL 20
2004-03-05 00:00:00 50 40 30
2004-03-06 00:00:00 NULL NULL 30
2004-03-07 00:00:00 NULL NULL 30
2004-03-08 00:00:00 NULL NULL 30
2004-03-09 00:00:00 NULL NULL 30
2004-03-10 00:00:00 NULL NULL 30
2004-03-11 00:00:00 NULL NULL 30
2004-03-12 00:00:00 NULL NULL 30
2004-03-13 00:00:00 NULL NULL 30
2004-03-14 00:00:00 NULL NULL 30
2004-03-15 00:00:00 NULL NULL 30