如何将字符串变量添加到jdbc firebird连接上的SQL查询

Question

I am trying to query a Firebird database from a Java application. This query contains 2 integer variables and 1 string. The query looks like this:

Statement statement = conn.createStatement();

ResultSet rs = statement.executeQuery("select * from table where
  column1 < " + intvariable1 + " and ( 
  column2 > " + intvariable2 +" or column2 = 0) and 
  column3 = '" + stringvariable + "' ";

Rs.next();
syso(rs.getInt(1));

It appears that the ResultSet is empty but when I use a hardcoded string value instead of a variable I get the expected result.

I also tried this with preparedstatements with the same result - it is only working without string variable.

Any ideas what I am doing wrong?

EDIT: Problem solved! The Stringvariable came from a BLOB Field and had some empty values within it. Calling the trim function deleted those.

Answer 1

I noticed that in the "column3" line you have a space after the opening quote and before the closing quote. Unless you are deliberately trying to match strings that start and end with a space, you won't find results. If not, cut out the spaces:

column3 = '" + stringvariable + "' ";