java - jdbc - how to select query in one string -

i trying fetch select queries in 1 string. want. tried different ways, not solve. code:

resultset rs = st.executequery("select city_id user name = '"    + name + "'");          string sql = "";         while (rs.next()) {             sql += "select * city id = " +rs.getint(1) + ",";         }         sql = sql.substring(0, sql.length()-1);              preparedstatement stmt = con.preparestatement(sql);         rs = stmt.executequery(); 

i did this, there errors. how can solve it? basically, want add many queries in 1 string, , execute string. need them in resultset.

i'm little confused trying achieve guess need this:

select * city c inner join user u on (c.id = u.city_id)  u.name = ?; 

then need execute 1 query , have desired results.

but @dystroy mentioned if want use approach need @ first fetch ids user list<integer> , create list<string> hold queries or use in clause in query.

pseudo-code:

// getting ids user  list<integer> cityids = new arraylist<integer>(); string query = "select city_id user name = ?"; preparedstatement ps = con.preparestatement(query); ps.setstring(1, name); resultset rs = ps.executequery(); while (rs.next()) {    cityids.add(rs.getint("city_id")); }  // dynamically create query  stringbuilder builder = new stringbuilder("select * city id in ("); (int = 0; < cityids.size(); i++) {    builder.append("?");    if (i < cityids.size() - 1) {       builder.append(",");    } } builder.append(")");  // creating preparedstatement  ps = con.preparestatement(builder.tostring());  // adding params query  int index = 1; (integer id: cityids) {    ps.setint(index, id);    index++; }  resultset rs = ps.executequery(); while (rs.next()) {    // stuff } 

note: recommend use parametrized statements provide more safer dealing database, more human-readable , efficient.