• 1.建立資料庫表及插入資料
• 2.子查詢統計不同性質的學生總數
• 3.一行資料轉換成兩列資料 union all
• 4.錶行列資料轉換(錶轉置)

建立資料庫、建立學生表並設定主鍵、插入資料程式碼如下：

--建立資料庫  
create database StudentMS  
  
--使用資料庫  
use StudentMS  

--建立學生表 (屬性:姓名、學號(pk)、學院、出生日期、性別、籍貫)  
create table xs  
(  
    name varchar(10) not null,  
    id varchar(10) not null,  
    xy varchar(10),  
    birthday datetime,  
    xb char(2),  
    jg varchar(8)  
)  

--建立學生表主鍵:學號  
alter table xs  
    add constraint  
pk_xs primary key(id)  

--插入資料
insert into xs   
    (id, name, xb, birthday, xy, jg)   
values('1160001', '劉備', '男', '1991-11-5', '軟體學院', '河北省');   
 

2.子查詢統計不同性質的學生總數

使用子查詢統計不同學院總人數、不同性別總人數和河北/河南學生總人數。

--子查詢統計人數  
select a.a_num as 軟院人數, b.b_num as 計院人數, c.c_num as 自動化人數,   
       d.d_num as 男生人數, e.e_num as 女生人數, f.f_num as 河北河南人數  
from  
(select count(*) as a_num from xs where xy='軟體學院') a,  
(select count(*) as b_num from xs where xy='計算機學院') b,  
(select count(*) as c_num from xs where xy='自動化學院') c,  
(select count(*) as d_num from xs where xb='男') d,  
(select count(*) as e_num from xs where xb='女') e,  
(select count(*) as f_num from xs where jg in ('河北省','河南省')) f;  
 

3.一行資料轉換成兩列資料

這時，專案SQL語句的需要是顯示成兩列如下圖所示：

select '軟院人數' as "統計類別", count(*) as "數量" from xs where xy='軟體學院'
union all
select '計院人數', count(*) from xs where xy='計算機學院'
union all
select '自動化人數', count(*) from xs where xy='自動化學院'
union all
select '男生人數', count(*) from xs where xb='男'
union all
select '女生人數', count(*) from xs where xb='女'
union all
select '河北河南人數', count(*) from xs where jg in ('河北省','河南省');
 

select whxs1.num1 as 專案名稱,  whxs2.num2 as 數量
from
(select decode(KWHD_WH_XZ, '校級', '校級總數', KWHD_WH_XZ) as num1
from T_WSTB_KWHD_1 t
where KWHD_WH_XZ='校級'
group by KWHD_WH_XZ) whxs1,
(select sum(decode(t.KWHD_WH_XZ,'校級',1,0)) as num2
from T_WSTB_KWHD_1 t
where KWHD_WH_XZ='校級'
group by KWHD_WH_XZ ) whxs2;

4.錶行列資料轉換(錶轉置)

select country, sum(case when type='A' then money end) as A,
sum(case when type='B' then money end) as B,
sum(case when type='C' then money end) as C
from table1
group by country

decode(條件,值1,結果1,值2,結果2,值3,結果3,... 值n,結果n,預設值)

函式類比：
IF 條件=值1 THEN
　　　　RETURN(結果1)
ELSIF 條件=值2 THEN
　　　　RETURN(結果2)
　　　　......
ELSIF 條件=值n THEN
　　　　RETURN(結果n)
ELSE
　　　　RETURN(預設值)
END IF

select
name as 姓名,sum(decode(t.result,'勝',1,0)) as 勝,sum(decode(t.result,'負',1,0)) as 負
from t_result t
group by name
order by 勝 desc,負 asc