寫SQL語句時候,特別是需要套用公式的時候,我們可能需要一些自增序列作爲參數測試,然後通過公式生成想用的結果集;
如:
銀行存款, 每期利息::; 本金*(利率+0.001*期數)然後我們需要統計前20期的情況;
select
name as '姓名',
money as '本金',
term as '期數',
money*(0.09+0.001*term) as '利息'
from
(
select "王三" as name,5000 as money
) as save
join
(
select
@tm:=@tm+1 as term -- 期數
from tbl_student,(select @tm:=0) as t
limit 20
)as tx
查詢結果:
王三 5000 1 455
王三 5000 2 460
王三 5000 3 465
王三 5000 4 470
王三 5000 5 475
王三 5000 6 480
王三 5000 7 485
王三 5000 8 490
王三 5000 9 495
王三 5000 10 499.99999999999994
王三 5000 11 504.99999999999994
王三 5000 12 509.99999999999994
王三 5000 13 515
王三 5000 14 520
王三 5000 15 525
王三 5000 16 530
王三 5000 17 535
王三 5000 18 540
王三 5000 19 545
王三 5000 20 550
若是要前20期利息和:我們就有根據了
select
姓名,
本金,
sum(利息) as 前20期利息和
from
(
select
name as '姓名',
money as '本金',
term as '期數',
money*(0.09+0.001*term) as '利息'
from
(
select "王三" as name,5000 as money
) as save
join
(
select
@tm:=@tm+1 as term -- 期數
from tbl_student,(select @tm:=0) as t
limit 20
)as tx
)as tbl
結果:
王三 5000 10050