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)' ;
原文链接：https://www.f2er.com/oracle/210355.html