Question

I want to execute one of the two queries here based on a parameter.
The parameter could be a Yes/No Flag. Based on ‘Yes’ value, first query should get executed, and so as the second based on ‘No’.

SELECT per.PERSONAL_NUM as EMP_NUM,per.FIRST_NAME||' '||MIDDLE_NAME||' '||LAST_NAME AS NAME,per.EMPLOYEE_TYPE
  FROM PER_EMPLOYEE_MST per
  WHERE FIRST_NAME LIKE (:pname)||'%'

  UNION ALL 

  SELECT dep.DEPUT_PERS_NUM as EMP_NUM,dep.FIRST_NAME||' '||MIDDLE_NAME||' '||LAST_NAME AS NAME,dep.EMPLOYEE_TYPE
  FROM PER_DEPUTATION_MST dep
  WHERE FIRST_NAME LIKE (:pname)||'%'

  ORDER BY NAME

Answer 1

Make checking the flag part of the WHERE clause of each part, so they will return no rows if they aren’t appropriate:

SELECT per.PERSONAL_NUM as EMP_NUM,per.FIRST_NAME||' '||MIDDLE_NAME||' '||LAST_NAME AS NAME,per.EMPLOYEE_TYPE FROM PER_EMPLOYEE_MST per WHERE FIRST_NAME LIKE (:pname)||'%' AND :flag = 1

UNION ALL

SELECT dep.DEPUT_PERS_NUM as EMP_NUM,dep.FIRST_NAME||' '||MIDDLE_NAME||' '||LAST_NAME AS NAME,dep.EMPLOYEE_TYPE FROM PER_DEPUTATION_MST dep WHERE FIRST_NAME LIKE (:pname)||'%' AND :flag = 0

ORDER BY NAME