plsql块执行ddl语句

学习：

http://www.cnblogs.com/huanghai223/archive/2011/06/29/2093660.html

declare

  v_count integer := 0;

begin

  select count(1) into v_count from user_constraints where constraint_name = 'SYS_C008270';

  if (v_count > 0) then

    --prd

    execute immediate 'alter table tfz_grade_detail_rec_his drop constraint SYS_C008270';

  else

    --stg

    execute immediate 'alter table tfz_grade_detail_rec_his drop constraint SYS_C008170';

  end if;

end;