const char *sql = "select c.contentid,c.contenttext,c.indexid,i.title from book_content c left join book_index i where c.indexid = i.indexid and c.indexid = ?";请问最后的c.indexid = ?是什么意思?
调试欢乐多
?后续会用一个变量代替,可以防止SQL注入