SQL 難點解決：序列生成

1、    生成連續整數序列

MySQL8:  with recursive t(n) as (

select 1

union all

select n+1 from t where n<7

)

select * from t;

Oracle：select level n

from dual connect by level<=7;

集算器 SPL：

A1：構造從 1 到 7 的整數序列

示例 1：百雞問題，雞翁一值錢五，雞母一值錢三，雞雛三值錢一。百錢買百雞，問雞翁、母、雛各幾

MySQL8:  

with recursive jg(n) as (select 1 union all select n+1 from jg where n<100/5),

jm(n) as (select 1 union all select n+1 from jm where n<100/3),

jc(n) as (select 3 union all select n+3 from jc where n<98)

select jg.n jw, jm.n jm, jc.n jc

from jg cross join jm cross join jc

where jg.n*5+jm.n*3+jc.n/3=100 and jg.n+jm.n+jc.n=100

集算器 SPL：

A1：構造1到20的整數序列

A2：構造1到33的整數序列

A3：構造1到99且步長為3的整數序列

A4：建立資料結構為(jw,jm,jc)的序表

A5：對A1、A2、A3的資料進行巢狀迴圈，若滿足於A1成員+A2成員+A3成員==100且A1成員*5+A2成員*3+A3成員/3==100則追加到A4序表中

示例2：將指定列中冒號分隔的串劃分成多行

Oracle:

with t(k,f) as (select 1 , 'a1:a2:a3' from dual

union all select 2, 'b1:b2' from dual),

t1 as (select k,f, length(f)-length(replace(f,':',''))+1 cnt from t),

t2 as (select level n from dual connect by level<=(select max(cnt) from t1)),

t3 as (select t1.k, t1.f, n, cnt,

case when n=1 then 1 else instr(f,':',1,n-1)+1 end p1, 

case when n=cnt then length(f)+1 else instr(f,':',1,n) end p2

from t1 join t2 on t2.n<=t1.cnt)

select k,substr(f,p1,p2-p1) f from t3 order by k;

集算器 SPL：

A1：建立資料結構為(k,f)的序表，並追加2條記錄(1, “a1:a2:a3)和(2,”b1:b2”)

A2：將A1的欄位f用冒號劃分成序列並重新賦值給欄位f

A3：針對A1每條記錄構造資料結構為(k,f)的序表，並根據欄位f中成員構造記錄(A1.k，f成員)追加到此序表中

2、    生成連續日期序列

MySQL8：

with recursive

t(d) as (select date'2018-10-03'

union all

select d+1 from t where d<date'2018-10-09')

select d,dayofweek(d) w from t;

集算器 SPL：

A1：生成2018-10-03到2018-10-09的日期序列

示例：列出2015-01-03到2015-01-07每天的銷量彙總

MySQL8：

with recursive

t(d,v) as (select date'2015-01-04',30

union all select date'2015-01-06',50

union all select date'2015-01-07',50

union all select date'2015-01-03',40

union all select date'2015-01-04', 80),

s(d) as (select date'2015-01-03'

union all

select d+1 from s where d<date'2015-01-07')

select s.d, sum(t.v) v

from s left join t on s.d=t.d

group by s.d;

集算器 SPL：

A4：A2中記錄按欄位d的值對齊到A3

A5：根據A4和A3對位構造統計後的序表

3、    生成連續的工作日(不包含週六週日)序列

MySQL8:

with recursive

t(d) as (select date'2018-10-03'

union all

select d+1 from t where d<date'2018-10-09')

select d,dayofweek(d) w from t

where dayofweek(d)<=5;

集算器 SPL：

       A1：構造從2018-10-03到2018-10-09不包含週六週日的日期序列

       A2：根據A1構造日期及相應周幾的序表

4、    根據序列生成表

MySQL8：

with recursive t1(n) as (select 1 union all select n+1 from t1 where n<14),

t2(n, name) as (select n, concat('a',n) name from t1)

select max(if(n%4=1, name, null)) f1,

max(if(n%4=2, name, null)) f2,

max(if(n%4=3, name, null)) f3,

max(if(n%4=0, name, null)) f4

from t2

group by floor((n+3)/4);

集算器 SPL：