1 常用函数

count()-计数

sum()-求和

min(),max()-最值

avg()-平均值

day()-取时间字段的天值，同理还有month(), year()…Access有DateValue()函数，可以根据字段内容转换成相应格式的日期。

hex()-十进制转为十六进制

left(a,b)-返回字符串a左起b个字符的部分。同理还有right()（关于中文字是1个字符还是2个字符的问题，与数据库的定序(COLLATE)有关，用的时候问下程序就行。）

举例

SELECT count(*) as 计数,sum([Money]) as 总和,min([Money]) as 最小值,max([Money]) as 最大值,avg([Money]) as 平均值

FROM dbo_MoneyLog_2009_05

WHERE ((dbo_MoneyLog_2009_05.[why])=”任务添加”)

2 Group by子句

将查询结果按照Group by后面的内容进行分类，比如Group by [ID],Group by day([Time])

举例

SELECT day(TIME) as 日期,count(*) as 次数

FROM dbo_MoneyLog_2009_05

WHERE ((dbo_MoneyLog_2009_05.[why])=”捡到晶石”) group by day([TIME])

3 UNION 操作符

用来合并多个select语句的结果，合并的select列数必须一致。统计的时候常常用来将月份数据合并来统计年度数据。(不过话说月度数据出来了用excel统计年度数据更方便一点…)

使用上UNION ALL会列出所有的值，而UNION不会列出重复的值

举例

select [Times] as 时间,sum([counts]) AS 次数, Sum([Moneys]) AS 金额

from(SELECT DateValue([Time]) as times,count(*) AS counts, Sum([Money]) AS moneys

FROM dbo_MoneyLog_2009_04

where [why]=”捡到晶石”

group by DateValue([Time])

UNION ALL

SELECT DateValue([Time]) as times,count(*) AS counts, Sum([Money]) AS moneys

From dbo_MoneyLog_2009_05

where [why]=”捡到晶石”

GROUP BY DateValue([Time]))

Group by [Times]