As bakman2 says you need to drop the msg.
But if you want the brackets add them to template.
Here is example
[{"id":"65f7b5c6.940324","type":"inject","z":"efbbf209f839382a","name":"","props":[{"p":"id","v":"[1,2,3,4]","vt":"json"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","x":120,"y":880,"wires":[["f457b018.1681c"]]},{"id":"f457b018.1681c","type":"template","z":"efbbf209f839382a","name":"","field":"payload","fieldType":"msg","format":"handlebars","syntax":"mustache","template":"SELECT * FROM [dbo].[alert] WHERE id IN ({{{id}}})","output":"str","x":350,"y":860,"wires":[["72dc466d.4afbb"]]},{"id":"72dc466d.4afbb","type":"debug","z":"efbbf209f839382a","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":640,"y":880,"wires":[]}]
SELECT * FROM [dbo].[alert] WHERE id IN ({{{id}}})