I have a table with a attribute which i set it to varchar(20),
for example,
create account(
username varchar(20)
);
then i insert some data, then i want to do some comparision,

"select * from account where username="gadsfasdfhaskdfkasjdghfsdaf";

where "gadsfasdfhaskdfkasjdghfsdaf" has more than 20 characters,

when i run the query, error occurs, said that the value is invalid,

how can i solve the problem? is there any way to let it compare with a larger value?

the error is because of the quotes
"select * from account where username="gadsfasdfhaskdfkasjdghfsdaf";
should be
"select * from account where username='gadsfasdfhaskdfkasjdghfsdaf' ";
in this case, it does not return an error

Yeah, that was just an example,
actually i'm using JDBC and use preparedStatement to generate the query

for example
String name="asdfasq34radfalsdfb93hrlkawdfiah";
String query="select * from account where username=? "
PreparedStatment ps=con.prepareStatment(query);
ps.setString(1,name);
ps.executeQuery();

i've tried the entire query to execute manually in a command prompt,
it works, but it just can't work when i execute the query using PreparedStatement, is it the JDBC error? or other matters?

When you prepare the statement, DB2 allocates memory for the parameter based on the column data type, which is VARCHAR(20). If you later try to stuff a longer string into that parameter it won't fit, hence the error.

ic...
so is there any way to solve this problem?
thanks

What do you reallyyy want to achieve? Comparing a VARCHAR(20) with you value will always be false.

What exactly is the error raised by DB2? I just tried something similar on the command line, and it just worked (and returned 0 rows). No error condition was encountered.