[英]SQL queries in Java: (JDBC) How to use the SELECT statement?
This is my query to connect to my database. 这是我连接到我的数据库的查询。
SELECT naam, kleur, sector, aantalZilverstukken, Spel_naam
FROM speler
WHERE Spel_Naam = ?
I work in the console of netbeans. 我在netbeans的控制台工作。 When I want to show the records of table Speler with the Spel_Naam.
当我想用Spel_Naam显示表Speler的记录时。
In the console I want to type a primary key of the table Spel and then it shows me the records of the table Speler in the console. 在控制台中,我想键入表Spel的主键,然后它显示控制台中Speler表的记录。 How can I do this.
我怎样才能做到这一点。
Like WHERE Spel_Naam = ?
喜欢
WHERE Spel_Naam = ?
The question mark need to be the name that I typed in 问号必须是我输入的名称
Is the select statement correct? select语句是否正确? I want to type the Spel_Naam in the console and then It must connect to the database and give me the records of table Speler.
我想在控制台中键入Spel_Naam然后它必须连接到数据库并给我表Speler的记录。 How can I do this?
我怎样才能做到这一点?
public class SpelerMapper
{
private final static String LEES_SPELERS_SQL = "SELECT naam, kleur, sector, aantalZilverstukken, Spel_naam FROM speler WHERE Spel_Naam = ?";
public List<Speler> geefSpelers()
{
List<Speler> spelerLijst = new ArrayList<Speler>();
Statement statement;
Connection connection = PersistentieController.getInstance().getConnection();
try
{
statement = connection.createStatement();
// query database
ResultSet resultSet = statement.executeQuery(LEES_SPELERS_SQL);
while (resultSet.next())
{
String naam = resultSet.getString("naam");
String kleur = resultSet.getString("kleur");
int sector = resultSet.getInt("sector");
int aantalZilverstukken = resultSet.getInt("aantalZilverstukken");
Speler speler = new Speler(naam ,kleur, sector , aantalZilverstukken);
spelerLijst.add(speler);
}
statement.close();
return spelerLijst;
} catch (SQLException e)
{
e.printStackTrace();
}
return null;
}
Use PreparedStatement
s: 使用
PreparedStatement
:
String LEES_SPELERS_SQL = "SELECT ... WHERE Spel_Naam = ?";
PreparedStatement prepStmt = con.prepareStatement(LEES_SPELERS_SQL);
prepStmt.setString(1, naam);
ResultSet rs = prepStmt.executeQuery();
Additional note: while being another option, concatenation of the SQL query is an unsafe way of doing the same task. 附加说明:作为另一种选择,SQL查询的连接是执行相同任务的不安全方式。 Refer to this article for more info.
有关详细信息,请参阅此文章。
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