How to convert Persian (shamsi) date to Gregorian in T-SQL? - tsql

Question

I Use A lot data stored in Database to make a report and I was wondering if there is a fast way to convert all of the date in the tables to Persian date when selecting them.
there is some ways to convert but they aren't SQL based and so they are slower than a function just in the SQL.
so if any body knows how to do the converting in the SQL I will thank him a lot.

Answer 1

And a day of searching I decided to do my own style of solving.
and the result is here: Enjoy :D
USE [Test]
GO
/****** Object: UserDefinedFunction [dbo].[MyG2J] Script Date: 10/11/2019 02:35:43 ب.ظ ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER FUNCTION [dbo].[MyG2J](#inputDate DateTime)
RETURNS nvarchar(max)
begin
declare #mDay int,#mMonth int,#mYear int,#sDay int,#sMonth int,#sYear int,#mid int, #isMC bit=0,#isSC bit=0,#preSC bit = 0;
set #mDay=day(#inputDate);
set #mMonth=MONTH(#inputDate);
set #mYear=YEAR(#inputDate);
if #mYear%4=0
set #isMC=1;
else
set #isMC=0;
set #sYear=#mYear-622;
if (#sYear+1)%4=0
set #preSC = 1;
else
set #preSC=0;
select #mid=
case
when #mMonth=1 then'20'
when #mMonth=2 then'19'
when #mMonth=3 then'20'
when #mMonth=4 then'20'
when #mMonth=5 then'21'
when #mMonth=6 then'21'
when #mMonth=7 then'22'
when #mMonth=8 then'22'
when #mMonth=9 then'22'
when #mMonth=10 then'22'
when #mMonth=11 then'21'
when #mMonth=12 then'21'
end
if #isMC=1
begin
set #mid=#mid-1
end
if #mMonth=3 and #mDay=#mid
set #sMonth=#mMonth+9;
else
begin
if (#mMonth=3 and #mDay>#mid) or (#mMonth>3)
begin
set #sYear=#sYear+1;
set #sMonth=#mMonth-3;
end
else
set #sMonth=#mMonth+9;
end
if (#sYear+1)%4=0
set #isSC = 1;
else
set #isSC=0;
if #isMC=1
BEGIN
if #isSC=0
if #mMonth!=3
set #mid=#mid+1
END
else
begin
if #isSC=1
if #mMonth!=3
set #mid=#mid-1
end
if #mDay>#mid
begin
set #sDay=#mDay-#mid;
set #sMonth=#sMonth+1;
end
else
begin
if #sMonth<7
set #sDay=31+(#mDay-#mid);
else
begin
if #sMonth=12
BEGIN
if #isSC=1
set #sDay=30+(#mDay-#mid);
else
set #sDay=29+(#mDay-#mid);
END
else
set #sDay=30+(#mDay-#mid);
end
end
return Cast(#sYear as nvarchar)+'/'+Cast(#sMonth as nvarchar)+'/'+Cast(#sDay as nvarchar)
end