SQL Server 2014

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CREATE FUNCTION GetStringCount(@strValue VARCHAR(MAX), @strCount VARCHAR(MAX))
RETURNS INT
AS
BEGIN
  RETURN ISNULL((DATALENGTH(@strValue) - 
    DATALENGTH(REPLACE(@strValue COLLATE Latin1_General_CS_AS, @strCount, ''))) / 
    DATALENGTH(@strCount), 0);
END
CREATE TABLE example (
  col VARCHAR(MAX)
);

INSERT INTO example VALUES
  ('Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.'),
  ('At vero eos et accusam et justo duo dolores et ea rebum.'),
  ('Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.'),
  (NULL);
4 rows affected

SELECT dbo.GetStringCount('Hello', 'l');
SELECT dbo.GetStringCount('This costs 5$.', '$');
SELECT dbo.GetStringCount('This costs 5€.', '€');

(No column name)

2

(No column name)

1

(No column name)

1

SELECT *, dbo.GetStringCount(col, 'a') 
FROM example;

col
(No column name)

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
11

At vero eos et accusam et justo duo dolores et ea rebum.
3

Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
8

null
0

col	(No column name)
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.	11
At vero eos et accusam et justo duo dolores et ea rebum.	3
Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.	8
null	0