Please list all sale team names which had orders on 5/31/2018.
had orders on 5/31/2018 refer to OrderDate = '5/31/18'; sale team names refer to Sales Team;
SELECT T FROM ( SELECT DISTINCT CASE  WHEN T1.OrderDate = '5/31/18' THEN T2.`Sales Team` ELSE NULL END AS T FROM `Sales Orders` T1 INNER JOIN `Sales Team` T2 ON T2.SalesTeamID = T1._SalesTeamID ) WHERE T IS NOT NULL