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Code throws SQLException but SQL code execute successful [duplicate]

I have a Java-code:
String searchPerson = "select * from persons where surname like ? and name like ?";
//connect to DB
PreparedStatement statement = connect.prepareStatement(searchPerson);
statement.setString(1,"%"+ surname + "%");
statement.setString(2, "%" + name + "%");
ResultSet resultPerson = statement.executeQuery(searchPerson);
//..code
Then I have SQLException:
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 '?'

You should execute the PrepareStatement with no parameters as follows:
statement.executeQuery()
Calling executeQuery with a String parameter will execute the provided query as is (without the bound parameters).

ResultSet resultPerson = statement.executeQuery(searchPerson);
should be
ResultSet resultPerson = statement.executeQuery();

Try with statement.setString(1,"'%"+ surname + "%'");

Working on this Java project where I need to be able to delete data from the database on user's request

The query inside MySQL is working:
DELETE FROM f9.yoo
WHERE account_tags = '#8GGGJPUR9'
I can delete data inside MySQL, but the problem is whenever I try to remove the account_tags from my Java application, it throws an error:
java.sql.SQLSyntaxErrorException: 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 'DELETE FROM f9.yoo
WHERE account_tags = '#8GGGJPUR9'' at line 2
Here's my Java SQL query:
Statement statement = dbConnection.createStatement();
String sql = "SELECT * FROM "+databaseName+"."+tableName+";\n" +
"DELETE FROM "+databaseName+"."+tableName+"\n" +
"WHERE account_tags = '"+AccountTag+"';";
statement.executeQuery(sql);
The error isn't giving me much to work with, so I really have no idea what is wrong with the program.

Did you add the allowMultiQueries=true
If not then you can add that while you sending the connecting request to your database. So you need to append the allowMultiQueries=true in your to database URL.
Like this:
String dbUrl = "jdbc:mysql:///test?allowMultiQueries=true";

String sql = "DELETE FROM "+databaseName+"."+tableName+"\n" +
"WHERE account_tags = ?";
try (PreparedStatement statement = dbConnection.prepareStatement(sq)) {
statement.setString(1, AccountTag);
int updateCount = statement.executeUpdate();
System.out.printf("%s: %d records deleted.%n", tableName, updateCount);
}
The only thing used is the DELETE, for which one should use executeUpdate.
One definitely should use a PreparedStatement as many code checkers will give alarms otherwise. It escapes things like ', handles types of the arguments, and possible conversions, and especially is a security feature against SQL injection.
The System.out usage is bad style, better would be using a logger.
try-with-resources automatically closes the PreparedStatement even with a raised exception or break/return.
When doing both database operations, it seems better to use two (prepared) statements, as the first returns a ResultSet.
So:
String sql = SELECT * FROM "+databaseName+"."+tableName + "\n" +
"WHERE account_tags = ?";
try (PreparedStatement statement = dbConnection.prepareStatement(sq)) {
statement.setString(1, AccountTag);
try (ResultSet rs = statement.executeQuery()) {
...
}
}

Better to separate statements with an If condition :
String sql1="SELECT * FROM "+databaseName+"."+tableName;
String sql2="DELETE FROM "+databaseName+"."+tableName+" "+
"WHERE account_tags = '"+AccountTag+"';
statement.executeQuery(sql1);
statement.executeUpdate(sql2);

How to escape '&' symbol of Text in SQL WHERE Clause? [duplicate]

Trying to get started with JDBC (using Jetty + MySQL). I'm not sure how to escape user-supplied parameters in a SQL statement. Example:
String username = getDangerousValueFromUser();
Statement stmt = conn.createStatement();
stmt.execute("some statement where username = '" + username + "'"));
How do we escape "username" before use with a statement?

Use Prepared statement.
for example :
con.prepareStatement("update Orders set pname = ? where Prod_Id = ?");
pstmt.setInt(2, 100);
pstmt.setString(1, "Bob");
pstmt.executeUpdate();
It will prevent raw SQL injection
If you want to escape sql string then check for StringEscapeUtils.escapeSql(). Note that that this method was deprecated in Commons Lang 3.
Also See
does-using-preparedstatement-mean-there-will-not-be-any-sql-injection

Unknown column error in where clause, using MySQL and Java

Following is my code line :
ResultSet rs3 = stmt6.executeQuery("SELECT * FROM ShopSystem.Order where s_id="+s_id+" AND status="+Pending);
I am getting the following error :
Unknown column 'Pending' in 'where clause'
What could be the reason... I cant get through it..

No doubt, status is a string, so it needs to be compared to a string. Use delimiters:
SELECT * FROM ShopSystem.Order where s_id="+s_id+" AND status='"+Pending+"'"
Or better yet, learn how to write code that uses parameter substitution for putting parameter values into SQL strings.

Change it to
AND status = '" + Pending + "'"
You need to put the string in quotes. Otherwise the DB thinks you mean a column name.
But actually you should use Prepared Statements. Then you don't need to patch the queries together like this and you don't worry about parameters and escaping them...

Don't make concatenation ! Use prepared statements
PreparedStatement stm = conn.prepareStatement("SELECT * FROM ShopSystem.Order where s_id = ? AND status = ?");
stm.setInt(1, s_id);
stm.setString(2, Pending.name());
ResultSet rs = stm.executeQuery();

you must use the PreparedStatement in this case
// use the ? for the 2 entries values
String selectSQL = new String("SELECT * FROM ShopSystem.Order where s_id=? AND status=?")
preparedStatement = dbConnection.prepareStatement(selectSQL);
// in order you must incialise them here
preparedStatement.setString(1, "s_id");
preparedStatement.setString(2, "Pending");
//execute your resultset `enter code here`
ResultSet rs = preparedStatement.executeQuery();

right syntax to use near '?'

I have a Java-code:
String searchPerson = "select * from persons where surname like ? and name like ?";
//connect to DB
PreparedStatement statement = connect.prepareStatement(searchPerson);
statement.setString(1,"%"+ surname + "%");
statement.setString(2, "%" + name + "%");
ResultSet resultPerson = statement.executeQuery(searchPerson);
//..code
Then I have SQLException:
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 '?'

You should execute the PrepareStatement with no parameters as follows:
statement.executeQuery()
Calling executeQuery with a String parameter will execute the provided query as is (without the bound parameters).

ResultSet resultPerson = statement.executeQuery(searchPerson);
should be
ResultSet resultPerson = statement.executeQuery();

Try with statement.setString(1,"'%"+ surname + "%'");