03 模糊、分页、联合查询

String sql = "select * from emp where ename like ?";
pstat.setString(1,"%"+letter+"%");
String sql = "select * from emp where ename like \"%\" 字母 \"%\"";
pstat.setString(1,letter);

String sql = "select * from emp order by sal desc limit ?,每页显示几条";

String sql = "select * from emp e , dept d where e.deptno = d.deptno";
String sql = "select deptno,count(empno) as ct from emp group by deptno";