I have created table with 3 fields language,country,install type. When I write a query to print the maximum occuring value in each of the field, I am getting a weird problem.Can anyone say the reason.Here is my code.
PreparedStatement ps1= null;
ps1 = conn.prepareStatement("desc Configuration");
ResultSet rs1=ps1.executeQuery();
while(rs1.next()) {
System.out.print(rs1.getString(1)+":");
PreparedStatement ps2= null;
ps2 = conn.prepareStatement("select ? from Configuration c1 "+
" group by language "+
" having count(*) >= all " +
" ( select count(*) from Configuration c2 "+
" group by language )");
ps2.setString(1,rs1.getString(1));
ResultSet rs2=ps2.executeQuery();
while(rs2.next())
System.out.print(rs2.getString(1));
System.out.println();
}
The output I am getting here is language:language But the output what I am expecting is
language:english like that. I am getting later output if i replace '?' with language in the prepare statement.But if i give the same with ? I am getting what ever I have given for ps2.setString.
Why is this happening. Any solutions?
? in prepared statements is not a placeholder for textual substitution, it's a parameter, therefore its value is always interpreted as data, not as an arbitrary part of query syntax.
So, in this case the actual query being executed is an equivalent of select 'language' from ....
If you need to substitute parts of the query other than data, you have to use concatenation (beware of SQL injections!):
ps2 = conn.prepareStatement("select "
+ rs1.getString(1)
+ " from Configuration c1 group by language having count(*) >= all( select count(*)from Configuration c2 group by language )");
You can't set column names using a PreparedStatement. You can only set column values.
Instead of using this approach, you will have to build the sql yourself using concatenation, for example:
String sql = "select "+ rs1.getString(1) + " from Configuration c1 group by language having count(*) >= all( select count(*)from Configuration c2 group by language)";
The '?' mark in ps2 is recognized as literal-string. Not as a column name.
Related
I want to fetch data from exasol but only facing this issue when I use limit clause in query.
If i hardcode the limit values in query and don't use prepared statement for then it works fine. But when I try to set int for limit clause in prepared statement it gives me exception
public static final String FROM_DWB_DATA = "SELECT * FROM DWB_DATA a \n"
+ "INNER JOIN DWB_CONN b \n"
+ "ON a.SOURCE_ID=b.ID\n"
+ "WHERE b.PROJECT_ID=? ORDER BY a.TABLE_NAME LIMIT ? , ?";
//and in Prepared statement i am setting these values
PreparedStatement ps = getSQLConnection(projectId, conid)
.prepareStatement(FROM_DWB_DATA_TABLE);
ps.setString(1, projectId);
ps.setInt(2, 0);
ps.setInt(3, 2);
java.sql.SQLException: non-negative integer value expected in LIMIT clause
I guess, it adds your values in quoted form: LIMIT '0', '2'.
Try to build query string normally and run it as simple non-prepared query.
I am having code something like this.
final PreparedStatement stmt = connection
.prepareStatement("delete from " + fullTableName
+ " where name= ?");
stmt.setString(1, addressName);
Calculation of fullTableName is something like:
public String getFullTableName(final String table) {
if (this.schemaDB != null) {
return this.schemaDB + "." + table;
}
return table;
}
Here schemaDB is the name of the environment(which can be changed over time) and table is the table name(which will be fixed).
Value for schemaDB is coming from an XML file which makes the query vulnerable to SQL injection.
Query: I am not sure how the table name can be used as a prepared statement(like the name used in this example), which is the 100% security measure against SQL injection.
Could anyone please suggest me, what could be the possible approach to deal with this?
Note: We can be migrated to DB2 in future so the solution should compatible with both Oracle and DB2(and if possible database independent).
JDBC, sort of unfortunately, does not allow you to make the table name a bound variable inside statements. (It has its reasons for this).
So you can not write, or achieve this kind of functionnality :
connection.prepareStatement("SELECT * FROM ? where id=?", "TUSERS", 123);
And have TUSER be bound to the table name of the statement.
Therefore, your only safe way forward is to validate the user input. The safest way, though, is not to validate it and allow user-input go through the DB, because from a security point of view, you can always count on a user being smarter than your validation.
Never trust a dynamic, user generated String, concatenated inside your statement.
So what is a safe validation pattern ?
Pattern 1 : prebuild safe queries
1) Create all your valid statements once and for all, in code.
Map<String, String> statementByTableName = new HashMap<>();
statementByTableName.put("table_1", "DELETE FROM table_1 where name= ?");
statementByTableName.put("table_2", "DELETE FROM table_2 where name= ?");
If need be, this creation itself can be made dynamic, with a select * from ALL_TABLES; statement. ALL_TABLES will return all the tables your SQL user has access to, and you can also get the table name, and schema name from this.
2) Select the statement inside the map
String unsafeUserContent = ...
String safeStatement = statementByTableName.get(usafeUserContent);
conn.prepareStatement(safeStatement, name);
See how the unsafeUserContent variable never reaches the DB.
3) Make some kind of policy, or unit test, that checks that all you statementByTableName are valid against your schemas for future evolutions of it, and that no table is missing.
Pattern 2 : double check
You can 1) validate that the user input is indeed a table name, using an injection free query (I'm typing pseudo sql code here, you'd have to adapt it to make it work cause I have no Oracle instance to actually check it works) :
select * FROM
(select schema_name || '.' || table_name as fullName FROM all_tables)
WHERE fullName = ?
And bind your fullName as a prepared statement variable here. If you have a result, then it is a valid table name. Then you can use this result to build a safe query.
Pattern 3
It's sort of a mix between 1 and 2.
You create a table that is named, e.g., "TABLES_ALLOWED_FOR_DELETION", and you statically populate it with all tables that are fit for deletion.
Then you make your validation step be
conn.prepareStatement(SELECT safe_table_name FROM TABLES_ALLOWED_FOR_DELETION WHERE table_name = ?", unsafeDynamicString);
If this has a result, then you execute the safe_table_name. For extra safety, this table should not be writable by the standard application user.
I somehow feel the first pattern is better.
You can avoid attack by checking your table name using regular expression:
if (fullTableName.matches("[_a-zA-Z0-9\\.]+")) {
final PreparedStatement stmt = connection
.prepareStatement("delete from " + fullTableName
+ " where name= ?");
stmt.setString(1, addressName);
}
It's impossible to inject SQL using such a restricted set of characters.
Also, we can escape any quotes from table name, and safely add it to our query:
fullTableName = StringEscapeUtils.escapeSql(fullTableName);
final PreparedStatement stmt = connection
.prepareStatement("delete from " + fullTableName
+ " where name= ?");
stmt.setString(1, addressName);
StringEscapeUtils comes with Apache's commons-lang library.
I think that the best approach is to create a set of possible table names and check for existance in this set before creating query.
Set<String> validTables=.... // prepare this set yourself
if(validTables.contains(fullTableName))
{
final PreparedStatement stmt = connection
.prepareStatement("delete from " + fullTableName
+ " where name= ?");
//and so on
}else{
// ooooh you nasty haker!
}
create table MYTAB(n number);
insert into MYTAB values(10);
commit;
select * from mytab;
N
10
create table TABS2DEL(tname varchar2(32));
insert into TABS2DEL values('MYTAB');
commit;
select * from TABS2DEL;
TNAME
MYTAB
create or replace procedure deltab(v in varchar2)
is
LvSQL varchar2(32767);
LvChk number;
begin
LvChk := 0;
begin
select count(1)
into LvChk
from TABS2DEL
where tname = v;
if LvChk = 0 then
raise_application_error(-20001, 'Input table name '||v||' is not a valid table name');
end if;
exception when others
then raise;
end;
LvSQL := 'delete from '||v||' where n = 10';
execute immediate LvSQL;
commit;
end deltab;
begin
deltab('MYTAB');
end;
select * from mytab;
no rows found
begin
deltab('InvalidTableName');
end;
ORA-20001: Input table name InvalidTableName is not a valid table name ORA-06512: at "SQL_PHOYNSAMOMWLFRCCFWUMTBQWC.DELTAB", line 21
ORA-06512: at "SQL_PHOYNSAMOMWLFRCCFWUMTBQWC.DELTAB", line 16
ORA-06512: at line 2
ORA-06512: at "SYS.DBMS_SQL", line 1721
I am developing a java web service that is deployed in wildly. It is connected to a postgresql database.
In this database, I have a table called xx_activity. In it there is a column called "id", which is also the primary key.
Here is the query used to create the table:
CREATE TABLE xx_activity
(
id serial NOT NULL,
baseitemid integer
);
to connect to this table, I use the following java code:
conn = postgresVoyateDBConnection();
query = conn.prepareStatement("select id, baseitemid" +
"from xx_activity " +
"where \"id\" = ? ");
query.setInt(1, id);
ResultSet rs = query.executeQuery();
However, when I call the method that includes this code, I get an error:
org.postgresql.util.PSQLException: ERROR: column "id" does not exist
Position: 8
This is confusing because I certainly have this column. i added escape characters as per this answer, but it did not solve the issue.
Also note that queries without the where clause, like:
conn = postgresVoyateDBConnection();
query = conn.prepareStatement("select id, baseitemid " +
"from xx_activity");
ResultSet rs = query.executeQuery();
work perfectly.
I have also tried without using escape characters but it gives the same error. I also checked in pgadmin and there is no trailing space in the column name, neither are there any upper case letters involved (in which case, the other select query shouldn't have worked?).
How can this be fixed?
Fixed this, the issue was a missing space. After the first line of the query, there needs to be a space as belows:
query = conn.prepareStatement("select id, baseitemid " +
"from xx_activity " +
"where \"id\" = ? ");
EDIT: escape charactors not needed for id; so final answer should be:
query = conn.prepareStatement("select id, baseitemid " +
"from xx_activity " +
"where id = ? ");
Hi I'm doing a query in java, i have java and posgres connected with the driver 9.3-1102-jdbc41
This is my query: query = "SELECT * FROM" +"\"users\" "+ " where user="+"'"+name+"'"+"and pass =" +"'"+pass+"'";
when I run it, this error appears:
Relation "users name" doesn't exist
Here and in others sites a possible solution is checking the quotes or the capital letters.
But I´m sure about the capital letters and this is what I tried:
query = "SELECT * FROM" +"\"users\" "+ " where user="+"'"+name+"'"+"and pass =" +"'"+pass+"'";
query = "SELECT * FROM users where user="+"'"+name+"'"+"and pass =" +"'"+pass+"'";
query = "SELECT * FROM" +"\"sysmar.users\" "+ " where user="+"'"+name+"'"+"and pass =" +"'"+pass+"'";
Error relation users does not exist
"SELECT * FROM users where user="+name+"and pass =" +pass;
syntax error near to pass
Thanks in advance for your answers and time
try:
"SELECT * FROM users where \"user\" ='"+name+"'and pass ='" +pass+"'";
But it's harmful for sql injection. See PreparedStatements.
For PostgreSQL you shouldn't need to put quotes around the table name unless it's a reserved keyword. Users isn't a keyword, but user just so happens to be one of them.
Your query is hard enough to read with the extra concatenation operations and spacing issues. Perhaps there is a syntax error and you just need to clean it up:
q = "SELECT * FROM users WHERE \"user\" = '" + name + "' AND pass = '" + pass + "'";
You want the final evaluated string to look like (for example):
SELECT * FROM users WHERE "user" = 'cory' AND pass = '12345';
But as others have mentioned, you should also switch to using prepared statements. This code is probably vulnerable to SQL injection attacks.
You really shouldn't concatenate variables with SQL queries, you are becoming vulnerable to SQL injection then. You better be using Prepared Statements which will allow you to write queries in more readable and secure fashion.
Connection conn = DriverManager.getConnection(...);
String queryString = "SELECT * FROM users WHERE user = ? AND pass = ?";
PreparedStatement query = conn.prepareStatement(queryString);
query.setString(1, name);
query.setString(2, password);
ResultSet result = query.executeQuery();
I try to create a PreparedStatement:
stmt = conn.prepareStatement("SELECT POLBRP, POLTYP, POLNOP, INCPTP, TRMTHP, " +
"CLTKYP , CANDTP, POLSTP, EXPRYP, OINCPP, CANRNP, PAYMDP,
KCNFLP, KCRTSP, KACADP, KSCHMP, EXPRYP FROM "
+ POLHDR + " WHERE POLNOP = " + idNumber +
" AND POLBRP = " + branch + " AND POLTYP = " + product +
" AND OINCPP <= "+date );
And this throws an SQLException: [SQL0206] Column AD not in specified tables.
I have no idea where it's getting column AD from as I never specified it in the select clause (unless I'm being completely blind and stupid)
Can anyone help?
If your variables are strings, e.g. branch
" AND POLBRP = " + branch + " ...
then you forgot to quote the values
" AND POLBRP = '" + branch + "' ...
but the real solution is using placeholders
... AND POLBRP = ? ...
which would prevent such problems once and for all, this is what PreparedStatement is designed for
Try to change your query into this:
SELECT
POLBRP,
POLTYP,
POLNOP,
INCPTP,
TRMTHP,
CLTKYP,
CANDTP,
POLSTP,
EXPRYP,
OINCPP,
CANRNP,
PAYMDP,
KCNFLP,
KCRTSP,
KACADP,
KSCHMP,
EXPRYP
FROM TableName WHERE POLNOP = ? AND POLBRP = ? AND POLTYP = ? AND OINCPP <= ?";
Then use:
stmt.setString(1, "ValueOfPOLNOP");
...
When your query is being executed ? will be replaced with the value you passed into PreparedStatement#setString(int, String) method
Preventing SQL Injection in Java shows the proper use of PreparedStatement:
Prepared Statements Variables passed as arguments to prepared
statements will automatically be escaped by the JDBC driver.
Example: ps.1
String selectStatement = "SELECT * FROM User WHERE userId = ? ";
PreparedStatement prepStmt = con.prepareStatement(selectStatement);
prepStmt.setString(1, userId);
ResultSet rs = prepStmt.executeQuery();
From the same source, following in the same section:
Although Prepared Statements helps in defending against SQL Injection,
there are possibilities of SQL Injection attacks through inappropriate
usage of Prepared Statements. The example below explains such a
scenario where the input variables are passed directly into the
Prepared Statement and thereby paving way for SQL Injection attacks.
Example: ps.2
String strUserName = request.getParameter("Txt_UserName");
PreparedStatement prepStmt = con.prepareStatement("SELECT * FROM user WHERE userId = '+strUserName+'");