Spring JDBC：执行Order By时结果不一致

Question

任何帮助将不胜感激。我正在使用Spring JDBC进行数据访问的项目中，并且正在使用按列表示顺序的顺序执行简单查询，我目前得到的结果不一致，这意味着按顺序执行似乎不起作用。我尝试了多个数据库仍然无济于事。

String sql = "select * from account where upper(name) like upper(:query) order by name asc";
MapSqlParameterSource params = new MapSqlParameterSource().addValue("query", "%" + query + "%");

List<Account> accountsSearched = namedParameterJdbcTemplate.query(sql, params, new BeanPropertyRowMapper<Account>(Account.class));

任何想法可能是什么问题？

Answer 1

因此问题不在您的SQL代码内，但在搜索方法实现中存在问题”

现有代码

public List<Account> search(String uncleanedQuery, int offset) {
    String query = uncleanedQuery.replaceAll("([-+.^:,])","");
    String sql = "select * from account where upper(name) like upper(:query) order by name asc";
    MapSqlParameterSource params = new MapSqlParameterSource().addValue("query", "%" + query + "%");
    List<Account> accountsSearched = namedParameterJdbcTemplate.query(sql, params, new BeanPropertyRowMapper<Account>(Account.class));
    Set<Account> accountSearchSet = new HashSet<Account>(accountsSearched);
    List<Account> accounts = new ArrayList<Account>(accountSearchSet);
    return accounts;
}
在上面的代码中，我们正在正确地获取数据，但是将其分配给HashSet。 HashSet不遵循名称排序，而是为Account生成随机订单，因此您每次都会获得随机订单。

解决方案1：

没有理由，您实际上需要设置。使用set只会使程序变慢。如果要获取DISTINCT数据，请修改SQL查询。

public List<Account> search(String uncleanedQuery, int offset) {
    String query = uncleanedQuery.replaceAll("([-+.^:,])","");
    String sql = "select * from account where upper(name) like upper(:query) order by name asc";
    MapSqlParameterSource params = new MapSqlParameterSource().addValue("query", "%" + query + "%");
    List<Account> accountsSearched = namedParameterJdbcTemplate.query(sql, params, new BeanPropertyRowMapper<Account>(Account.class));
    return accountsSearched;
}
解决方案2：

仍然，您想使用您的方法，然后更改代码以使用TreeSet并根据名称进行排序

public List<Account> search(String uncleanedQuery, int offset) {
    String query = uncleanedQuery.replaceAll("([-+.^:,])", "");
    System.out.println("Search Query Called");
    String sql = "select * from account where upper(name) like upper(:query) order by name";

    MapSqlParameterSource params = new MapSqlParameterSource().addValue("query", "%" + query + "%");

    List<Account> accountsSearched = namedParameterJdbcTemplate.query(sql, params,
            new BeanPropertyRowMapper<Account>(Account.class));

    Comparator<Account> comp = new Comparator<Account>() {

        @Override
        public int compare(Account a1, Account a2) {
            return a1.getName().compareTo(a2.getName());
        }
    };

    SortedSet<Account> accountSearchSet = new TreeSet<Account>(comp);
    accountSearchSet.addAll(accountsSearched);

    List<Account> accounts = new ArrayList<Account>(accountSearchSet);

    return accounts;
}