oracle:
sqlstr := 'select count(tname) from tab where tname = ''' || tablename || '''';
等价于:sqlstr :=( 'select count(tname) from tab where tname = '' ' )|| tablename || (' '' ');
sqlstr :='create index ZC_' || tablename || '_SYFX on ' || tablename || ' (SYFX)';
等价于:sqlstr :='create index ZC_' || tablename || '_SYFX on ' || tablename || ' (SYFX)' ;