bryansis2010 bryansis2010 - 5 months ago 25
SQL Question

preparedStatement syntax error

I recently encountered this problem with Java PreparedStatements. I have the following code:

String selectSql1
= "SELECT `value` FROM `sampling_numbers` WHERE `value` < (?)" ;
ResultSet rs1 = con.select1(selectSql1,randNum);


where the
select1
method is

public ResultSet select1(String sql, int randNum) {
try {
this.stmt = con.prepareStatement(sql);
stmt.setInt(1, randNum);
return this.stmt.executeQuery(sql);
} catch (SQLException e) {
e.printStackTrace();
return null;
}
}


However, it keeps throwing this error:

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 '?)' at line 1
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1054)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4237)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4169)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2617)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2778)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2828)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2777)
at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1651)
at util.P_DBCon.select1(P_DBCon.java:59)
at app.RandomNumberGenerator.main(RandomNumberGenerator.java:60)

Exception in thread "main" java.lang.NullPointerException
at app.RandomNumberGenerator.main(RandomNumberGenerator.java:64)


This problem does not happen when I do the naive way of doing "...
value < " + randNum
but I would like to do so this way.

Any help is much appreciated.

UPDATE



I tried with the various recommendations by the community, like

String selectSql1
= "SELECT `value` FROM `sampling_numbers` WHERE value < ?" ;

String selectSql1
= "SELECT value FROM sampling_numbers WHERE value < ?" ;


and still the error message comes out.

Answer

The solution to your problem is actually very easy, you are calling Statement.executeQuery(String) when you want to call PreparedStatement.executeQuery() -

this.stmt = con.prepareStatement(sql); // Prepares the Statement.
stmt.setInt(1, randNum);               // Binds the parameter.
// return this.stmt.executeQuery(sql); // calls Statement#executeQuery
return this.stmt.executeQuery();       // calls your set-up PreparedStatement
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