refactor: if() to CASE WHEN (#31360)

* refactor: if() to CASE WHEN

* fix: remove duplicate order by

* fix: remove extraneous table

* style: reformat to black spec

Co-authored-by: Ankush Menat <ankush@frappe.io>
diff --git a/erpnext/controllers/status_updater.py b/erpnext/controllers/status_updater.py
index 76a25a0..197d2ba 100644
--- a/erpnext/controllers/status_updater.py
+++ b/erpnext/controllers/status_updater.py
@@ -443,7 +443,7 @@
 				"""update `tab%(target_parent_dt)s`
 				set %(target_parent_field)s = round(
 					ifnull((select
-						ifnull(sum(if(abs(%(target_ref_field)s) > abs(%(target_field)s), abs(%(target_field)s), abs(%(target_ref_field)s))), 0)
+						ifnull(sum(case when abs(%(target_ref_field)s) > abs(%(target_field)s) then abs(%(target_field)s) else abs(%(target_ref_field)s) end), 0)
 						/ sum(abs(%(target_ref_field)s)) * 100
 					from `tab%(target_dt)s` where parent='%(name)s' having sum(abs(%(target_ref_field)s)) > 0), 0), 6)
 					%(update_modified)s
@@ -455,9 +455,9 @@
 			if args.get("status_field"):
 				frappe.db.sql(
 					"""update `tab%(target_parent_dt)s`
-					set %(status_field)s = if(%(target_parent_field)s<0.001,
-						'Not %(keyword)s', if(%(target_parent_field)s>=99.999999,
-						'Fully %(keyword)s', 'Partly %(keyword)s'))
+					set %(status_field)s = (case when %(target_parent_field)s<0.001 then 'Not %(keyword)s'
+					else case when %(target_parent_field)s>=99.999999 then 'Fully %(keyword)s'
+					else 'Partly %(keyword)s' end end)
 					where name='%(name)s'"""
 					% args
 				)