在sql中增加case可以增加数据处理的灵活性，注意结尾的end

1 proc sql outobs=10; 2     title 'this is an example of sql and case'; 3     select wangnei,date, 4             case 5             when 200901<=date<=200903 then 'first' 6             when 200904<=date<=200906 then 'second' 7             else 'else' 8             end as season 9     from mysas.mmsone10     where date<=200912;11 quit;

 ---------sas 9.3 sql procedure user's guide page 35 or (49/418)

 在where字句后还可以加上许多operator

any all between-and contains exists in isnull is missing like =* 

in

1 proc contents data=mysas.ifthen;  2 run; 3 proc print data=mysas.ifthen (firstobs=1 obs=10); 4 run; 5 proc sql outobs=10; 6     title 'this is a instance of in'; 7     select * from mysas.ifthen 8     where date in(200901,200902) 9     order by shen descending;10 quit;

between and

1 proc sql outobs=10;2     title 'this is a try of between and';3     select * from mysas.ifthen4     where date between 200905 and 2010015     order by shen dscending;6 quit;

like

1 proc sql outobs=50;2     select * from &dataset3     where  subporduct_code like 'z%' or subporduct_code like 'XX____';4 quit;

 在where筛选条件中对于排序文本也可以用大于小于的逻辑来判断：eqt gtt ltt get let net.