I am working with a Java prepared statement that gets data from an Oracle database. Due to some performance problems, the query uses a "virtual column" as an index.
The query looks like this:
String status = "processed";
String customerId = 123;
String query = "SELECT DISTINCT trans_id FROM trans WHERE status = " + status + " AND FN_GET_CUST_ID(trans.trans_id) = " + customerId;
Connection conn = getConnection();
PreparedStatement ps = null;
ResultSet rs = null;
try {
ps = conn.prepareStatement(query);
ps.execute();
...
} catch (...)
This does not work. Having the function as part of the where clause causes a SQLException. I am aware of CallableStatement, and know I could use that first and then concatenate the results. However, this table uses FN_GET_CUST_ID(trans_id) as part of it's index. Is there a way to use a prepared statement with a database function as a query parameter?
Never concatenate arguments for the SQL into the String. Always use placeholders (?) and setXxx(column, value);.
You'll get the same error if you'd run the SQL in a your favorite DB tool. The problem is that Oracle can't use the function for some reason. What error code do you get?
If Customer ID is numeric keep in int not in String. Then try doing the following:
String query = "SELECT DISTINCT trans_id FROM trans WHERE status = ? AND FN_GET_CUST_ID(trans.trans_id) = ?";
ps = conn.prepareStatement(query);
ps.setString(1, status);
ps.setInt(2, customerId);
ps.execute();
Besides other benefits of prepared statement you won't have to remember about string quotations (this causes your error most likely) and escaping of the special characters.
At the first glance, the query seems to be incorrect. You are missing an apostrophe before and after the usage of status variable (assuming that status is a varchar column).
String query = "SELECT DISTINCT trans_id FROM trans
WHERE status = '" + status + "' AND FN_GET_CUST_ID(trans.trans_id) = " + customerId;
EDIT: I am not from java background. However, as #Aron has said, it is better to use placeholders & then use some method to set values for parameters to avoid SQL Injection.
Related
when i write database query :
select * from mytable WHERE subTitle='داتا باللغه العربيه';
it not return any thing but it is found in database table
Since you've included Java as a tag, I'll assume you're using JDBC for connecting to the database, in which case you should never be sending that particular string (SQL statement) to the database.
That is because that particular string implies string concatenation for building the SQL statement, as in:
String subtitle = "داتا باللغه العربيه";
String sql = "select * from mytable WHERE subTitle='" + subtitle + "'";
That is a very big no, no, because it leaves you vulnerable to SQL injection attacks.
Instead, you should be using a PreparedStatement and use parameters markers:
String subtitle = "داتا باللغه العربيه";
String sql = "select * from mytable WHERE subTitle=?";
try (PreparedStatement stmt = conn.prepareStatement(sql)) {
stmt.setString(1, subtitle);
try (ResultSet rs = stmt.executeQuery()) {
// use result set here
}
}
If this doesn't fix the character set issues you have, try using setNString instead. The 'N' is actually what you likely should have used for the string literal too, as in N'داتا باللغه العربيه', but don't use the string literal.
select * from mytable WHERE subTitle='داتا باللغه العربيه'
I am trying to run a SQL statement in Java and I am getting syntax
String number,key; //populate number and key.
rs = stmt.executeQuery("select count(*)
from users_transition
where phoneNumber =" +number +"and randKey="+key);
In MySQL database, phoneNumber is BigInt(20) and key is Int(11).
Also, according to this link. The table 5.1 says that types in MYSQl can be converted to what types in Java. Doesnt the other way round would work too?
Here's the ERROR
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 'randKey=9999' at line 1
You are missing a space between the number and the AND operator:
rs = stmt.executeQuery("select count(*) from users_transition where phoneNumber =" +number +" and randKey="+key);
// ^
You should replace the query with prepared statement, and use query parameters. This would help you not only avoid simple errors like this, but also make your code immune to SQL injection attacks.
String sql = "select count(*) from users_transition where phoneNumber =? and randKey=?";
PreparedStatement getCount = con.prepareStatement(sql);
getCount.setBigDecimal(1, new BigDecimal(number));
getCount.setBigDecimal(2, new BigDecimal(randKey));
I'll tell you what is wrong, and then I'll tell you what is very wrong.
What is wrong
First, you are building a query which where has missing spaces (and possibly missing quotes):
String number,key; //populate number and key.
rs = stmt.executeQuery("select count(*) "
+ "from users_transition "
+ "where phoneNumber =" +number +" and randKey="+key)";
// ^ you missed a space here
What is very wrong
Your query is vulnerable to SQL Injection Attacks (please read the link, it provides a humorous example and tips on solving the problem). Use prepared statements to do this kind of thing:
String number, key;
PreparedStatement ps = conn.prepareStatement("select count(*) "
+ "from users_transition "
+ "where phoneNumber=? "
+ " and randKey=?");
// The question marks are place holders for values
// You can assign this values with setXXX() methods
ps.setString(1, number);
ps.setString(2, randKey);
ResultSet rs = ps.executeQuery();
// Do whatever you need to do with the ResultSet
I keep getting this error when trying to connect to the database.
This is my prepared statement
String SQL = "SELECT * FROM `?` WHERE `HomeTeam` = '?'";
PreparedStatement prepst;
prepst = con.prepareStatement(SQL);
prepst.setString(1,box1.getSelectedItem().toString());
prepst.setString(2,box1.getSelectedItem().toString());
rs = prepst.executeQuery();
Anyone know why I get this error?
I think that your problem is in ' and ``` symbols. You should fix the sql as follwing:
String SQL = "SELECT * FROM ? WHERE HomeTeam = ?";
However I am not sure that parameter placeholder ? is supported after from. So, propbably you will have to put it yourself, e.g.:
String table = box1.getSelectedItem().toString();
String SQL = "SELECT * FROM " + table + " WHERE HomeTeam = ?";
Use
String SQL = "SELECT * FROM ? WHERE HomeTeam = ?";
Don't use ` to nest parameters, use ' to nest values you're comparing against if you're hard coding them.
You can't use ? to specify a table name.
I get a parameter is called 'id' in my function and want to print the cell of the name of this id row.
for example:
this is my table:
id name email
1 alon alon#gmail.com
I send to my function: func(1), so I want it to print 'alon'.
this is what I tried:
static final String url = "jdbc:mysql://localhost:3306/database_alon";
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(url, "root", "Admin");
String query_txt = "SELECT * FROM authors WHERE id = " + id;
Statement ps2 = con.createStatement();
ResultSet my_rs = ps2.executeQuery(query_txt);
System.out.println(my_rs.getString("name"));
con.close;
Everything is fine, but just one problem. You need to move your ResultSet cursor to the first row before fetching any values: -
Use: -
ResultSet my_rs = ps2.executeQuery(query_txt);
while (my_rs.next()) {
System.out.println(my_rs.getString("name"));
}
As a side note, consider using PreparedStatement to avoid getting attacked by SQL Injection.
Here's how you use it: -
PreparedStatement ps2 = con.prepareStatement("SELECT * FROM authors WHERE id = ?");
ps2.setInt(1, id);
ResultSet my_rs = ps2.executeQuery();
while (my_rs.next()) {
System.out.println(my_rs.getString("name"));
}
You need to use ResultSet.next() to navigate into the returned data:
if (my_rs.next()) {
System.out.println(my_rs.getString("name"));
}
Call my_rs.next(), which will move the ResultSet cursor onto the first row (which you are extracting data out of).
If this is a real application, use PreparedStatements instead of generic Statements. This is an extremely important matter of security if you plan on using user input in SQL queries.
I am trying to use a SQL Select statement for a query in Java. I currently have the following:
ResultSet rs = stmt.executeQuery("SELECT *" +
" FROM " + table +
" WHERE " + selection +
" VALUES " + selectionArgs);
where "selection" is a string and "selectionArgs" is a string array.
String selection = "documentFK=?";
String[] selectionArgs = { ... };
Is it possible to use the VALUES command to replace the ? like in with the INSERT command? Either way, what would be the correct syntax?
Thanks for the help.
I believe what you're looking for is the IN statement. Your query should look like this:
SELECT *
FROM table
WHERE documentFK IN ('doc1', 'doc2', 'doc3')
AND userFK IN ('user1', 'user2', 'user3')
This is (obviously) going to make your code a bit more ugly. You'll have to ensure that the WHERE keyword is used for the first clause, but the AND keyword is used for every other clause. Also, each list will have to be comma-delimited.
no, that is not the way it's done. first you create the statement from the query, using the question marks as place holders for the real values you want to put there. then you bind these values to the statement.
//the query
String sql = "SELECT " + "*" +
" FROM " + table +
" WHERE documetFK = ?";
//create the statement
PreparedStatement stmt = connection.prepareStatement(sql);
//bind the value
stmt.setInt(1, 4); //1 is "the first question mark", 4 is some fk
//execute the query and get the result set back
ResultSet rs = stmt.executeQuery();
now, if you want this thing with selection string and some args, then you're going to have a loop in your java code. not sure what your array looks like (you're not giving me that much to go on), but if it's made up from strings, it would be something like this:
//the query
String sql = "SELECT " + "*" +
" FROM " + table +
" WHERE " + selection;
//create the statement
PreparedStatement stmt = connection.prepareStatement(sql);
//bind the values
for(int i = 0; i < selectionArgs.length; i++) {
stmt.setString(i, selectionArgs[i]); //i is "the nth question mark"
}
//execute the query and get the result set back
ResultSet rs = stmt.executeQuery();
Can you use a PreparedStatement?
First of all SELECT .. WHERE .. VALUES is incorrect SQL syntax. Lose the VALUES part.
Then you're looking for prepared statements.
In your example it's going to look something like this:
String sql = "SELECT * FROM myTable WHERE documentFK=?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, "myDocumentFK"); // parameters start from 1, not 0. also we're assuming the parameter type is String;
ResultSet rs = pstmt.executeQuery();
Or with multiple parameters:
String sql = "SELECT * FROM myTable WHERE documentFK=? AND indexTerm=?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, "myDocumentFK"); // parameters start from 1, not 0. also we're assuming the parameter type is String;
pstsm.setInt(2, 100); // assume indexTerm can be 100 and is an integer
ResultSet rs = pstmt.executeQuery();
However, all of this doesn't worth your while since you can simply do the same by concatenating the value into the statement. But be aware of the SQL injections, so don't forget to escape the parameters that you're passing into the database.
PS: I was typing this way too long. You already have the answers :-)
As a side note, you may want to take a look at this to prevent SQL injections:
https://www.owasp.org/index.php/Preventing_SQL_Injection_in_Java
Sormula can select using "IN" operator from a java.util.Collection of arbitrary size. You write no SQL. It builds the SQL SELECT query with correct number of "?" parameters. See example 4.