SQL行列轉換例項

1.準備表和測試資料

create

table trandata (
id int
primary
key auto_increment,
flow_merc_id varchar(255),
tran_type varchar(255),
tran_amount int
);create
table trantype (
id int
primary
key auto_increment,
tran_type varchar(255)
);insert
into trantype (tran_type) values ('消費');
insert
into trantype (tran_type) values ('消費撤銷');
insert
into trantype (tran_type) values ('預授權完成');
insert
into trantype (tran_type) values ('預授權完成撤銷');
insert
into trantype (tran_type) values ('退貨');
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1000","消費",5);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1000","消費撤銷",1);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1000","消費",2);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1000","預授權完成",3);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1001","消費",4);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1001","消費",6);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1001","預授權完成撤銷",7);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1001","消費",9);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1002","消費",7);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1002","退貨",7);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1000","消費",2);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1003","消費",3);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1003","預授權完成",4);
insert
into trandata (flow_merc_id,tran_type,tran_amount) values ("1003","消費",5);

trandata表內容：

2.問題描述

問題一：

將相同flow_merc_id，相同tran_type的記錄合併，並算出交易筆數，交易金額的和。

select flow_merc_id as 商戶編號, tran_type as 交易型別, count(tran_type) as 交易筆數, sum(tran_amount) as 交易金額

問題二： 
統計出每個商戶的各種交易型別的交易筆數，交易金額。
select 

flow_merc_id as 商戶編號, 
count(tran_type) as 交易筆數, 
sum(tran_amount) as 交易金額,
sum(case tran_type when
'消費'
then
1else
0end ) 消費筆數,
sum(case tran_type when
'消費'
then tran_amount else
0end ) 消費,
sum(case tran_type when
'消費撤銷'
then
1else
0end ) 消費撤銷筆數,
sum(case tran_type when
'消費撤銷'
then tran_amount else
0end ) 消費撤銷,
sum(case tran_type when
'預授權完成'
then
1else
0end ) 預授權完成筆數,
sum(case tran_type when
'預授權完成'
then tran_amount else
0end ) 預授權完成,
sum(case tran_type when
'預授權完成撤銷'
then
1else
0end )預授權完成撤銷筆數,
sum(case tran_type when
'預授權完成撤銷'
then tran_amount else
0end )預授權完成撤銷,
sum(case tran_type when
'退貨'
then
1else
0end ) 退貨筆數,
sum(case tran_type when
'退貨'
then tran_amount else
0end ) 退貨
補充： case … when …then … else 也可以用if函式替換:
if(expr1,expr2,expr3) -->  if(tran_type='消費',1,0)
 
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