Variables in TSQL XML

How to use variables in TSQL XML methods

In order to search XML in TSQL using a variable, use the sql:variable("@VAR") format...

DECLARE @MYVAR INT = 1
SELECT * FROM [MYTABLE] WHERE [XMLCOL].exist('/data/item=sql:variable("@MYVAR")') = 1

If you're using the modify method, then you need to include it within curly braces...

DECLARE @MYVAR INT = 1
UPDATE [MYTABLE] SET [XMLCOL].modify('insert <item>{sql:variable("@MYVAR")}</item> as last into /data[1]')