title: Postgresql Dynamic SQL Query Execution
body: <p>I have a function which generates a SELECT query dynamically using some If Else conditions .I have stored that query in a TEXT type variable as </p>
  
  <pre><code>    CREATE OR REPLACE FUNCTION func_updateanswercodes(ans_id_param BIGINT, 
                                que_id_param BIGINT, 
                                overwrite_param INTEGER, 
                                new_ans_code_param CHARACTER VARYING)
      RETURNS INTEGER AS
      $BODY$
  ...................
  ................
  ...................
          dyn_sql = 'SELECT ' || que_col_name || ' INTO old_ans_col_val FROM';
                      IF SUBSTR(que_col_name, 0, 8) = 'pro_ans' THEN
                          dyn_sql = dyn_sql || ' profile_answers JOIN registrations ON (pro_ans_frn_pro_id = reg_frn_pro_id)';
                          ELSIF SUBSTR(que_col_name, 0, 8) = 'reg_ans' THEN
                          dyn_sql = dyn_sql || ' reg_answers ';
                          ELSIF SUBSTR(que_col_name, 0, 8) = 'tvl_ans' THEN
                          dyn_sql = dyn_sql || ' tvl_answers '; --35
                                  END IF;
                      dyn_sql = dyn_sql || ' WHERE';
                      IF SUBSTR(que_col_name, 0, 8) = 'pro_ans' THEN
                          dyn_sql = dyn_sql || ' reg_id ';
                          ELSIF SUBSTR(que_col_name, 0, 8) = 'reg_ans' THEN
                          dyn_sql = dyn_sql || ' reg_ans_frn_reg_id ';
                          ELSIF SUBSTR(que_col_name, 0, 8) = 'tvl_ans' THEN
                          dyn_sql = dyn_sql || ' tvl_ans_frn_reg_id ';
                                  END IF;
                          dyn_sql = dyn_sql || '= ' || CAST(temp_reg AS VARCHAR) ||';'
  
      /* Here want to execute that query in variable dync_sql
  ...........................
  .............................
  .......................
      END;
      $BODY$
      LANGUAGE plpgsql VOLATILE
  </code></pre>
  
  <p>But with plpgsql(PL/SQL for postgres) I don't know how to execute this same query in a variable . Please help me with this .
  Thanks in Advance</p>