SQL Server Equivalent to ORACLE INSTR - sql

Question

I wanted to know if in SQL Server there is an equivalent to the Oracle INSTR function?
I know that there is CHARINDEX and PATINDEX, but with the Oracle version I can also specify the Nth appearance of the character(s) I am looking for.
Oracle INSTR:
instr( string1, string2 [, start_position [, **nth_appearance** ] ] )
The CHARINDEX almost gets me there, but I wanted to have it start at the nth_appearance of the character in the string.

Answer 1

You were spot on that nth_appearance does not exist in SQL Server.
Shamelessly copying a function (Equivalent of Oracle's INSTR with 4 parameters in SQL Server) created for your problem (please note that #Occurs is not used the same way as in Oracle - you can't specify "3rd appearance", but "occurs 3 times"):
CREATE FUNCTION udf_Instr
(#str1 varchar(8000), #str2 varchar(1000), #start int, #Occurs int)
RETURNS int
AS
BEGIN
DECLARE #Found int, #LastPosition int
SET #Found = 0
SET #LastPosition = #start - 1
WHILE (#Found < #Occurs)
BEGIN
IF (CHARINDEX(#str1, #str2, #LastPosition + 1) = 0)
BREAK
ELSE
BEGIN
SET #LastPosition = CHARINDEX(#str1, #str2, #LastPosition + 1)
SET #Found = #Found + 1
END
END
RETURN #LastPosition
END
GO
SELECT dbo.udf_Instr('x','axbxcxdx',1,4)
GO
DROP FUNCTION udf_Instr
GO

Answer 2

Here is a version of Oracle's INSTR function which also works with a negative position for a reverse lookup as per Oracle's Doc here :- https://docs.oracle.com/cd/B28359_01/olap.111/b28126/dml_functions_1103.htm#OLADM564
CREATE FUNCTION dbo.INSTR(#str NVARCHAR(MAX), #substr NVARCHAR(MAX), #position INT = 1, #occurance INT = 1)
RETURNS INT
AS
BEGIN
DECLARE #loc INT = #position;
IF #loc < 0
BEGIN
SET #str = REVERSE(#str);
SET #substr = REVERSE(#substr);
SET #loc = #loc * -1;
END
IF #loc > 0
BEGIN
SET #loc = #loc - 1;
END
WHILE (#occurance > 0 AND CHARINDEX(#substr, #str, #loc + 1) > 0)
BEGIN
SET #loc = CHARINDEX(#substr, #str, #loc + 1);
SET #occurance = #occurance - 1;
END
IF #occurance > 0
BEGIN
SET #loc = 0;
END
IF #position < 0
BEGIN
SET #loc = LEN(#str) - #loc;
END
RETURN #loc
END

Answer 3

Change #str1 varchar(8000), #str2 varchar(1000) to #str1 varchar(1000), #str2 varchar(8000)
or
change CHARINDEX(#str1, #str2, #LastPosition + 1) to CHARINDEX(#str2, #str1, #LastPosition + 1)

Answer 4

You can use the following UDF (inline function rather than scalar)
CREATE FUNCTION dbo.INSTR
(
#str VARCHAR(8000),
#Substr VARCHAR(1000),
#start INT ,
#Occurance INT
)
RETURNS TABLE
AS
RETURN
WITH Tally (n) AS
(
SELECT TOP (LEN(#str)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
FROM (VALUES (0),(0),(0),(0),(0),(0),(0),(0)) a(n)
CROSS JOIN (VALUES(0),(0),(0),(0),(0),(0),(0),(0),(0),(0)) b(n)
CROSS JOIN (VALUES(0),(0),(0),(0),(0),(0),(0),(0),(0),(0)) c(n)
CROSS JOIN (VALUES(0),(0),(0),(0),(0),(0),(0),(0),(0),(0)) d(n)
)
, Find_N_STR as
(
SELECT
CASE WHEN DENSE_RANK() OVER(PARTITION BY #Substr ORDER BY (CHARINDEX(#Substr ,#STR ,N))) = #Occurance
THEN MAX(N-#start +1) OVER (PARTITION BY CHARINDEX(#Substr ,#STR ,N) )
ELSE 0
END [Loc]
FROM Tally
WHERE CHARINDEX(#Substr ,#STR ,N) > 0
)
SELECT Loc= MAX(Loc)
FROM Find_N_STR
WHERE Loc > 0
How to use:
declare #T table
(
Name_Level_Class_Section varchar(25)
)
insert into #T values
('Jacky_1_B2_23'),
('Johnhy_1_B2_24'),
('Peter_2_A5_3')
select t.Name_Level_Class_Section , l.Loc
from #t t
cross apply dbo.INSTR (t.Name_Level_Class_Section, '_',1,2) l

Answer 5

Try this !!
CREATE FUNCTION dbo.INSTR (#str VARCHAR(8000), #substr VARCHAR(255), #start INT, #occurrence INT)
RETURNS INT
AS
BEGIN
DECLARE #found INT = #occurrence,
#pos INT = #start;
WHILE 1=1
BEGIN
-- Find the next occurrence
SET #pos = CHARINDEX(#substr, #str, #pos);
-- Nothing found
IF #pos IS NULL OR #pos = 0
RETURN #pos;
-- The required occurrence found
IF #found = 1
BREAK;
-- Prepare to find another one occurrence
SET #found = #found - 1;
SET #pos = #pos + 1;
END
RETURN #pos;
END
GO
Usage :
-- Find the second occurrence of letter 'o'
SELECT dbo.INSTR('Moscow', 'o', 1, 2);
-- Result: 5