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Editor to share with you how to achieve mysql every N lines to generate a summary line, I believe that most people do not know much, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

There are three ways to deal with the need to generate a summary line every N lines

Select when c is null then 'summarize' else 'end spark ifnull (cMagneSumc) c from (

Select ceil (id/3) lg.cPol null sumc

From

(

Select @ id:=@id+1 id, t 1.* from t T1, (select @ id:=0) vars

) T2

Union all

Select ceil (id/3) lrecast nullpeng from

(

Select @ id1:=@id1+1 id, t 1.* from t T1, (select @ id1:=0) vars

) T3

Group by l

) t order by lpentry if null (cpendium 9999')

Results:

The second move is to complete the digital auxiliary watch. The performance is good. Calculating summary lines is a little more complicated to understand.

First add a digital auxiliary table nums

Table (int null) delimiter $$

Procedure pCreateNumscnt)

Declare s default

Truncate nums while s = intoselect

Set=+

End

$

Create (intbegin

Int 1 table

Insert nums s while S2 = intoselect+from

Set=*

End

$

Initialize the digital auxiliary table

Select if null (cmencc) c

From (

Select

When rn is null then 'summary' else''end s

T4.c

If (mod (t3.idjol 4)! = 0, when @ total=-1 then @ total:=t4.c else @ total:=@total+t4.c end,@total) cc

When mod (t3.idPol 4) = 0 then @ total:=-1 else null end

From (

Select * from nums where id

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