请教SQL的一个语句

SAS里的一段程序
Proc SQL NOPRINT;
select trim(left(put(count(name),8.))) into : trt1 - : trt3
From two
Group by department;
QUIT;

请问trim(left(put(count(name),8.))) 这段话里每个关键字的作用是什么？



proc sql noprint;
select compress(name)||'='|| trim(left(substr(name,3)))|| '_'||'MN'
into :mnlist
separated by ‘ ‘
from sashelp.vcolumn
where libname='PLAN' and memname='HDATA' and type=’num’ and name not in
(‘V1PATID’);
QUIT；

请问compress(name)||'='|| trim(left(substr(name,3)))|| '_'||'MN' 这段话的作用（每个关键字）是什么。