这段存储过程是什么意思 求详解

declare @PID INT
        declare @PtID INT
   
        declare @Num VARCHAR (10)
        select @Num = U_Num  from UserInfo where U_ID = @UID        
    if @BusiID =0
    BEGIN
        declare @BID INT
        select @BID = MAX(ID) +1 from dbo.Busi_Operate
        if @BID is null
        set @BID = 1
        set @PID = 0
        set @PtID = 0
        BEGIN tran
        exec Busi_Person_Save @PID out,@PersonName,@PersonSex,@PersonWork ,@Personnation
        ,@PersonPID,@PersonAge,@Personmail,@PersonAddress,@ProblemAddress ,@Persontel
        ,@PersonPhone,@IsSecret
        
        if @PID <=0
        BEGIN
            rollback tran
            select -1,'操作失败Busi_Person_Save'
            return -1
        END
        declare @mes VARCHAR (100)
        exec Busi_Petition_Save @PtID out ,@PetitionAim,@PetitionProblem,@PetitionUnionPerson
            ,@PetitionPersonNum ,@PetitionObjPerson ,@PetitionType ,@mes out
        if @PtID <=0
        BEGIN
            rollback tran
            select -2,'操作失败Busi_Petition_Save'+@mes
            return -2
        END            

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