Question

我试图通过java执行上面的查询，但我在第6行得到以下错误：

Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '? AND lexicon_lemma = ?)' at line 1
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:377)
at com.mysql.jdbc.Util.getInstance(Util.java:360)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:978)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3887)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3823)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2435)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2582)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2526)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2484)
at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1446)

我无法找到语法问题...有什么建议吗？这是我的问题：

public static void InsertEntry(String lexiconType, String lemma, String lang) throws SQLException {
    String selectSQL = "SELECT id FROM lexicons WHERE (lexicon_type = ? AND lexicon_lemma = ?)";
    PreparedStatement preparedStatement = connection.prepareStatement(selectSQL);
    preparedStatement.setString(1, lexiconType);
    preparedStatement.setString(2, lemma);
    ResultSet rs = preparedStatement.executeQuery(selectSQL);
    int id = -1;
    if (rs.next()) {
        id = rs.getInt(1);
        System.out.println(id);
    } else {
        String insertSQL = "INSERT INTO lexicons "
    + "(lexicon_type,lexicon_lemma,lexicon_lang) VALUES"
    + "(?,?,?)";
        PreparedStatement prepStatement = connection.prepareStatement(insertSQL);
        prepStatement.setString(1, lexiconType);
        prepStatement.setString(2, lemma);
        prepStatement.setString(3, lang);
        prepStatement .executeUpdate();
        prepStatement.close();
    }
}

Answer 1

没有必要将{1}}的sql语句变量传递给executeQuery。这是你案件中的主要问题。

PreparedStatement

当您重置要执行的sql时，该语句不会被识别为预准备语句，而是父PreparedStatement preparedStatement = connection.prepareStatement(selectSQL); preparedStatement.setString(1, lexiconType); preparedStatement.setString(2, lemma); // error is in the following statement ResultSet rs = preparedStatement.executeQuery(selectSQL);的实例，它正在查找引号之间的有效输入以查找等等哪些不存在。因此是语法错误。

更改：

Statement

致：

ResultSet rs = preparedStatement.executeQuery(selectSQL);

它应该有效。

参考：

PreparedStatement.html#executeQuery

Answer 2

更改：

ResultSet rs = preparedStatement.executeQuery(selectSQL);

到

ResultSet rs = preparedStatement.executeQuery();

线程＆＃34; main＆＃34;中的例外情况com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException：SQL语法中有错误

2 个答案: