Question

ps=ct.prepareStatement("select * from users where username like '% ? % '"); ps.setString(1,uname);

异常如下：
java.sql.SQLException: Parameter index out of range (1 > number of parameters, w
hich is 0).

Answer 1

口诀：

单双加
单百双加

一句搞定
ps=ct.prepareStatement("select * from users where username like '%"+ uname +"%'");

Answer 2

ps=ct.prepareStatement("select * from users where username like ？");

ps.setString(1,"%"+uname+“%”);