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91 lines
2.4 KiB
SAS
91 lines
2.4 KiB
SAS
/**
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@file
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@brief Returns all children from a hierarchy table for a specified parent
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@details Where data stores hierarchies in a simple parent / child mapping,
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it is not always straightforward to extract all the children for a
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particular parent. This problem is known as a recursive self join. This
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macro will extract all the descendents for a parent.
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Usage:
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data have;
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p=1;c=2;output;
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p=2;c=3;output;
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p=2;c=4;output;
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p=3;c=5;output;
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p=6;c=7;output;
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p=8;c=9;output;
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run;
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%mp_recursivejoin(base_ds=have
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,outds=want
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,matchval=1
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,parentvar=p
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,childvar=c
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)
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@param base_ds= base table containing hierarchy (not modified)
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@param outds= the output dataset to create with the generated hierarchy
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@param matchval= the ultimate parent from which to filter
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@param parentvar= name of the parent variable
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@param childvar= name of the child variable (should be same type as parent)
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@param mdebug= set to 1 to prevent temp tables being dropped
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@returns outds contains the following variables:
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- level (0 = top level)
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- &parentvar
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- &childvar (null if none found)
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@version 9.2
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@author Allan Bowe
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**/
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%macro mp_recursivejoin(base_ds=
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,outds=
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,matchval=
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,parentvar=
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,childvar=
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,iter= /* reserved for internal / recursive use by the macro itself */
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,maxiter=500 /* avoid infinite loop */
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,mDebug=0);
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%if &iter= %then %do;
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proc sql;
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create table &outds as
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select 0 as level,&parentvar, &childvar
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from &base_ds
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where &parentvar=&matchval;
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%if &sqlobs.=0 %then %do;
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%put NOTE: &sysmacroname: No match for &parentvar=&matchval;
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%return;
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%end;
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%let iter=1;
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%end;
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%else %if &iter>&maxiter %then %return;
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proc sql;
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create table _data_ as
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select &iter as level
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,curr.&childvar as &parentvar
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,base_ds.&childvar as &childvar
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from &outds curr
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left join &base_ds base_ds
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on curr.&childvar=base_ds.&parentvar
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where curr.level=%eval(&iter.-1)
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& curr.&childvar is not null;
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%local append_ds; %let append_ds=&syslast;
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%local obs; %let obs=&sqlobs;
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insert into &outds select distinct * from &append_ds;
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%if &mdebug=0 %then drop table &append_ds;;
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%if &obs %then %do;
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%mp_recursivejoin(iter=%eval(&iter.+1)
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,outds=&outds,parentvar=&parentvar
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,childvar=&childvar
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,base_ds=&base_ds
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)
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%end;
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%mend;
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