（排班表一）使用SQL语句使数据从坚向排列转化成横向排列

知识重点：

1.extract(day from schedule01::timestamp)=13

Extract 属于 SQL 的 DML（即数据库管理语言）函数，同样，InterBase 也支持 Extract，它主要用于从一个日期或时间型的字段内抽取年、月、日、时、分、秒数据，因此，它支持其关健字 YEAR、MONTH、DAY、HOUR、MINUTE、SECOND、WEEKDAY、YEARDAY。

　　Extract 的使用语法为：

　　 EXTRACT（关健字 FROM 日期或时间型字段）

　　如：extract(year from schedule01)=2017从日期中提取年份

2.max()函数：取最大值

3.case()函数的嵌套

　　注意嵌套case()函数时，每个case的开始和结束。

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排班功能：现有两个人员(A和B)，他们在不同日期的值班状态(state)不同，现在要查询他们在2017.6月的值班信息

表结构如下：

 CREATE TABLE public.temp_schedule

 (

   id integer NOT NULL DEFAULT nextval('temp_schedule_id_seq'::regclass),

   schedule01 timestamp without time zone,--日期

   schedule03 character varying(),--姓名

   state character varying(),--值班状态(0休 1班)

   CONSTRAINT temp_schedule_pkey PRIMARY KEY (id)

 )

1.查询SQL语句：

 select schedule03,schedule01,state  from temp_schedule

  where extract(year from schedule01)= and extract(month from schedule01)=

  order by  schedule03,schedule01;

显示为：

2.现在需要根据(6月的)日期，从1号开始根据人员名称横向合并排列数据(即只显示两行)

显示效果如下：

实现的SQL语句如下：

 select schedule03 as name

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day1

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day2

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day3

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day4

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day5

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day6

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day7

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day8

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day9

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day10

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day11

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day12

 ,max(case when extract(day from schedule01::timestamp)= then state end) as day13

 from temp_schedule

 where extract(year from schedule01)= and extract(month from schedule01)=

 group by schedule03;

3.将人员的值班状态通过汉字(0休 1班)显示出来，显示效果如下：

SQL语句(主要是实现case的嵌套)：

 select schedule03 as name

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day1

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day2

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day3

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day4

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day5

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day6

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day7

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day8

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day9

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day10

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day11

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day12

 ,max(case when extract(day from schedule01::timestamp)= then (case when state='' then '休' else '班' end) end) as day13

 from temp_schedule

 where extract(year from schedule01)= and extract(month from schedule01)=

 group by schedule03 ;

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