（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(255),--姓名

  state character varying(255),--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)=2017 and extract(month from schedule01)=6

 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)=1 then state end) as day1

,max(case when extract(day from schedule01::timestamp)=2 then state end) as day2

,max(case when extract(day from schedule01::timestamp)=3 then state end) as day3

,max(case when extract(day from schedule01::timestamp)=4 then state end) as day4

,max(case when extract(day from schedule01::timestamp)=5 then state end) as day5

,max(case when extract(day from schedule01::timestamp)=6 then state end) as day6

,max(case when extract(day from schedule01::timestamp)=7 then state end) as day7

,max(case when extract(day from schedule01::timestamp)=8 then state end) as day8

,max(case when extract(day from schedule01::timestamp)=9 then state end) as day9

,max(case when extract(day from schedule01::timestamp)=10 then state end) as day10

,max(case when extract(day from schedule01::timestamp)=11 then state end) as day11

,max(case when extract(day from schedule01::timestamp)=12 then state end) as day12

,max(case when extract(day from schedule01::timestamp)=13 then state end) as day13

from temp_schedule

where extract(year from schedule01)=2017 and extract(month from schedule01)=6

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)=1 then (case when state='0' then '休' else '班' end) end) as day1

,max(case when extract(day from schedule01::timestamp)=2 then (case when state='0' then '休' else '班' end) end) as day2

,max(case when extract(day from schedule01::timestamp)=3 then (case when state='0' then '休' else '班' end) end) as day3

,max(case when extract(day from schedule01::timestamp)=4 then (case when state='0' then '休' else '班' end) end) as day4

,max(case when extract(day from schedule01::timestamp)=5 then (case when state='0' then '休' else '班' end) end) as day5

,max(case when extract(day from schedule01::timestamp)=6 then (case when state='0' then '休' else '班' end) end) as day6

,max(case when extract(day from schedule01::timestamp)=7 then (case when state='0' then '休' else '班' end) end) as day7

,max(case when extract(day from schedule01::timestamp)=8 then (case when state='0' then '休' else '班' end) end) as day8

,max(case when extract(day from schedule01::timestamp)=9 then (case when state='0' then '休' else '班' end) end) as day9

,max(case when extract(day from schedule01::timestamp)=10 then (case when state='0' then '休' else '班' end) end) as day10

,max(case when extract(day from schedule01::timestamp)=11 then (case when state='0' then '休' else '班' end) end) as day11

,max(case when extract(day from schedule01::timestamp)=12 then (case when state='0' then '休' else '班' end) end) as day12

,max(case when extract(day from schedule01::timestamp)=13 then (case when state='0' then '休' else '班' end) end) as day13

from temp_schedule

where extract(year from schedule01)=2017 and extract(month from schedule01)=6

group by schedule03 ;

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