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)' ;