diff --git a/erpnext/accounts/doctype/tax_rule/tax_rule.py b/erpnext/accounts/doctype/tax_rule/tax_rule.py
index 9c091e8..2e92e05 100644
--- a/erpnext/accounts/doctype/tax_rule/tax_rule.py
+++ b/erpnext/accounts/doctype/tax_rule/tax_rule.py
@@ -130,8 +130,8 @@
 def get_tax_template(posting_date, args):
 	"""Get matching tax rule"""
 	args = frappe._dict(args)
-	conditions = ["""(from_date is null  or from_date = '' or from_date <= '{0}')
-		and (to_date is null  or to_date = '' or to_date >= '{0}')""".format(posting_date)]
+	conditions = ["""(from_date is null or from_date <= '{0}')
+		and (to_date is null or to_date >= '{0}')""".format(posting_date)]
 
 	for key, value in args.iteritems():
 		if key=="use_for_shopping_cart":
diff --git a/erpnext/controllers/queries.py b/erpnext/controllers/queries.py
index 53f9ecb..139586f 100644
--- a/erpnext/controllers/queries.py
+++ b/erpnext/controllers/queries.py
@@ -257,7 +257,7 @@
 def get_batch_no(doctype, txt, searchfield, start, page_len, filters):
 	cond = ""
 	if filters.get("posting_date"):
-		cond = "and (ifnull(batch.expiry_date, '')='' or batch.expiry_date >= %(posting_date)s)"
+		cond = "and (batch.expiry_date is null or batch.expiry_date >= %(posting_date)s)"
 
 	batch_nos = None
 	args = {
diff --git a/erpnext/patches/v7_1/set_currency_exchange_date.py b/erpnext/patches/v7_1/set_currency_exchange_date.py
index 7d8e4f0..630b7d4 100644
--- a/erpnext/patches/v7_1/set_currency_exchange_date.py
+++ b/erpnext/patches/v7_1/set_currency_exchange_date.py
@@ -5,5 +5,5 @@
 	frappe.db.sql("""
 		update `tabCurrency Exchange` 
 		set `date` = '2010-01-01' 
-		where date is null or date = '' or date = '0000-00-00'
+		where date is null or date = '0000-00-00'
 	""")
\ No newline at end of file
diff --git a/erpnext/patches/v7_2/rename_att_date_attendance.py b/erpnext/patches/v7_2/rename_att_date_attendance.py
index f7caf70..b2658ba 100644
--- a/erpnext/patches/v7_2/rename_att_date_attendance.py
+++ b/erpnext/patches/v7_2/rename_att_date_attendance.py
@@ -7,7 +7,7 @@
 	frappe.reload_doc("hr", "doctype", "attendance")
 	frappe.db.sql("""update `tabAttendance` 
 	 		set attendance_date = att_date
-			where attendance_date is null or attendance_date = '' or attendance_date = '0000-00-00'""")
+			where attendance_date is null or attendance_date = '0000-00-00'""")
 	
 	update_reports("Attendance", "att_date", "attendance_date")
 	update_users_report_view_settings("Attendance", "att_date", "attendance_date")
diff --git a/erpnext/patches/v7_2/update_salary_slips.py b/erpnext/patches/v7_2/update_salary_slips.py
index 22bb1d8..c6bca8e 100644
--- a/erpnext/patches/v7_2/update_salary_slips.py
+++ b/erpnext/patches/v7_2/update_salary_slips.py
@@ -9,8 +9,7 @@
 
 	salary_slips = frappe.db.sql("""select month, name, fiscal_year from `tabSalary Slip`
 				where (month is not null and month != '') and
-				(start_date is null  or start_date = '') and
-				(end_date is null  or end_date = '') and docstatus != 2""", as_dict=True)
+				start_date is null and end_date is null and docstatus != 2""", as_dict=True)
 
 	for salary_slip in salary_slips:
 		if not cint(salary_slip.month):