string ls_aa1.select * from a_table where nvl(aa,0)=nvl(:ls_aa,0);2.select * from a_table where nvl(aa,'')=nvl(:ls_aa,'');3.select * from a_table where (aa is null or aa=:ls_aa);4.select * from a_table where aa like '%' or aa is null;5.select * from a_table where nvl(aa,0) like '%';
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