passing java string variable in mysql query

Question

How to pass java string variable in sql query .I have done all the JDBC connection .

My sql database query is

sql = \"Select * 
       from productio         


        

Answer 1

String locationnames = "taplejung";

String sql = "Select * from production AS cust INNER JOIN location AS comp ON cust.location_id = comp.location_id where comp.name ='"+ locationnames +"' AND crop_id =1";

Answer 2

Use a PreparedStatement and bind the String parameter,

final String sql = "select * from production AS cust INNER JOIN location"
    + " AS comp ON cust.location_id = comp.location_id where "
    + "comp.name = ? AND crop_id = 1";
PreparedStatement ps = null;
try {
  ps = conn.prepareStatement(sql);
  ps.setString(1, "taplejung");
} catch (Exception e) {
  e.printStackTrace();
} finally {
  if (ps != null) {
    try {
      ps.close();
    } catch (Exception ignored) {
    }
  }
}

Edit (Based on your additional code, change it to something like)

PreparedStatement ps = null;

String sql = null;
if (cropnames.equals("paddy")) {
  // System.out.println();
  sql = "SELECT * FROM `production` AS cust INNER JOIN location AS comp "
      + "ON cust.location_id = comp.location_id WHERE comp.name = "
      + "? AND crop_id = 1";
} else {
  sql = "SELECT * FROM `production` WHERE crop_id = 4 AND location_id = 10";
}
ps = conn.prepareStatement(sql);
if (cropnames.equals("paddy")) {
  ps.setString(1, locationnames);
}
System.out.println(sql);
ResultSet rs = ps.executeQuery();

Answer 3

Passing variable is quiet simple in mysql query using java.

• Write your query
• and write the variable in ""
• In my case i am passing 'conition' and 'tablename' dynamically.

• Thank you very much have a good day.

  @Override public LinkedList getNameList(String condition, String tableName, String projectName) { // TODO Auto-generated method stub

  String query = "select distinct("+condition+") as name  from "+tableName+" ";
  
  //System.out.println(query);
  
  ResultSet rs = null;
  PreparedStatement preparedStatement = null;
  Connection connection = null;
  
  LinkedList finalList = new LinkedList();
  try{
      connection = dataSourceAbacus.getConnection();
      preparedStatement = connection.prepareStatement(query);
      rs= preparedStatement.executeQuery();
      while(rs.next()){
  
          finalList.add(rs.getString("name"));
      }
  }catch(Exception e){
      e.printStackTrace();
  }finally{
      if(connection !=null){
          try {
              connection.close();
          } catch (SQLException e) {
              // TODO Auto-generated catch block
              e.printStackTrace();
          }
      }
      if(preparedStatement != null){
          try{
              preparedStatement.close();
          }catch(Exception e){
              e.printStackTrace();
          }
      }
      if(rs != null){
          try{
              rs.close();
          }catch(Exception e){
              e.printStackTrace();
          }
      }
  }
  
  return finalList;
  

  }

Answer 4

Whenever I have to make sql queries I use a library like jdbi to do it. This will allow you to create an interface with different queries. All you have to do is define the interface, create a POJO, and create a mapper between a SQL table and a Java POJO.

The interface would look something like this.

@RegisterMapper(ProductionMapper.class)
public interface ProductionDAO {
     @SqlQuery("Select * from production AS cust INNER JOIN location AS comp ON cust.location_id = comp.location_id where comp.name = :name AND crop_id =1")
     Production findRow(@Bind("name") String name);
    } 

The POJO would look something like this.

public class Production {
   private VariableTypeA variableA;
   // other variables
   public Production(VariableTypeA variableA ....) {
      this.variableA = variableA;
      // set everything else
   }
   // getters and setters
}

The mapper would look something like this.

public class ProductionMapper implements ResultSetMapper<Production> {
  public Production map(int index, ResultSet r, StatementContext ctx) throws SQLException {
    return new Production(r.getSomeType("columnName"), ...);
  }
}

This design makes it really simple to interact with your database and pass variables as well as making it so that your classes dont violate the SRP

http://jdbi.org/sql_object_overview/