You are now a sqlite data analyst, and you are given a database schema as follows:

    【Schema】
    【DB_ID】 codebase_community
【Schema】
# Table: votes
[
(Id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(PostId:INTEGER, Examples: [3, 2, 5]),
(VoteTypeId:INTEGER, Examples: [2, 5, 3]),
(CreationDate:DATE, Examples: [2010-07-19]),
(UserId:INTEGER, Examples: [58, 6, 66]),
(BountyAmount:INTEGER, Examples: [50, 25, 0])
]
# Table: tags
[
(Id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(TagName:TEXT, Examples: [bayesian, prior, elicitation]),
(Count:INTEGER, Examples: [1342, 168, 6]),
(ExcerptPostId:INTEGER, Examples: [20258, 62158, 67815]),
(WikiPostId:INTEGER, Examples: [20257, 62157, 67814])
]
# Table: posts
[
(Id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(PostTypeId:INTEGER, Examples: [1, 2, 7]),
(AcceptedAnswerId:INTEGER, Examples: [15, 59, 5]),
(CreaionDate:DATETIME, Examples: [2010-07-19 19:12:12]),
(Score:INTEGER, Examples: [23, 22, 54]),
(ViewCount:INTEGER, Examples: [1278, 8198, 3613]),
(Body:TEXT),
(OwnerUserId:INTEGER, Examples: [8, 24, 18]),
(LasActivityDate:DATETIME, Examples: [2010-09-15 21:08:26]),
(Title:TEXT),
(Tags:TEXT, Examples: [<bayesian><prior><elicitation>]),
(AnswerCount:INTEGER, Examples: [5, 7, 19]),
(CommentCount:INTEGER, Examples: [1, 4, 2]),
(FavoriteCount:INTEGER, Examples: [14, 8, 36]),
(LastEditorUserId:INTEGER, Examples: [88, 183, 23]),
(LastEditDate:DATETIME, Examples: [2010-08-07 17:56:44]),
(CommunityOwnedDate:DATETIME, Examples: [2010-07-19 19:13:28]),
(ParentId:INTEGER, Examples: [3, 7, 6]),
(ClosedDate:DATETIME, Examples: [2010-07-19 20:19:46]),
(OwnerDisplayName:TEXT, Examples: [user28, user209, Michael Bishop]),
(LastEditorDisplayName:TEXT, Examples: [user28, user10525, sjcockell])
]
# Table: users
[
(Id:INTEGER, Primary Key, Examples: [-1, 2, 3]),
(Reputation:INTEGER, Examples: [1, 101, 6792]),
(CreationDate:DATETIME, Examples: [2010-07-19 06:55:26]),
(DisplayName:TEXT, Examples: [Community, Geoff Dalgas, Jarrod Dixon]),
(LastAccessDate:DATETIME, Examples: [2010-07-19 06:55:26]),
(WebsiteUrl:TEXT),
(Location:TEXT, Examples: [on the server farm, Corvallis, OR, New York, NY]),
(AboutMe:TEXT),
(Views:INTEGER, Examples: [0, 25, 22]),
(UpVotes:INTEGER, Examples: [5007, 3, 19]),
(DownVotes:INTEGER, Examples: [1920, 0, 5]),
(AccountId:INTEGER, Examples: [-1, 2, 3]),
(Age:INTEGER, Examples: [37, 35, 28]),
(ProfileImageUrl:TEXT)
]
# Table: postHistory
[
(Id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(PostHistoryTypeId:INTEGER, Examples: [2, 1, 3]),
(PostId:INTEGER, Examples: [1, 2, 3]),
(RevisionGUID:TEXT, Examples: [e58bf7fd-e60f-4c58-a6e4-dfc91cf98a69]),
(CreationDate:DATETIME, Examples: [2010-07-19 19:12:12]),
(UserId:INTEGER, Examples: [8, 24, 18]),
(Text:TEXT),
(Comment:TEXT),
(UserDisplayName:TEXT, Examples: [user28, user209, Michael Bishop])
]
# Table: comments
[
(Id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(PostId:INTEGER, Examples: [3, 5, 9]),
(Score:INTEGER, Examples: [5, 0, 11]),
(Text:TEXT),
(CreationDate:DATETIME, Examples: [2010-07-19 19:15:52]),
(UserId:INTEGER, Examples: [13, 37, 5]),
(UserDisplayName:TEXT, Examples: [user28, Statprof, jjgibaja])
]
# Table: postLinks
[
(Id:INTEGER, Primary Key, Examples: [108, 145, 217]),
(CreationDate:DATETIME, Examples: [2010-07-21 14:47:33]),
(PostId:INTEGER, Examples: [395, 548, 375]),
(RelatedPostId:INTEGER, Examples: [173, 539, 30]),
(LinkTypeId:INTEGER, Examples: [1, 3])
]
# Table: badges
[
(Id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(UserId:INTEGER, Examples: [5, 6, 8]),
(Name:TEXT, Examples: [Teacher, Student, Editor]),
(Date:DATETIME, Examples: [2010-07-19 19:39:07])
]
【Foreign keys】
votes.PostId=posts.Id
votes.UserId=users.Id
tags.ExcerptPostId=posts.Id
posts.LastEditorUserId=users.Id
posts.OwnerUserId=users.Id
posts.ParentId=posts.Id
postHistory.PostId=posts.Id
postHistory.UserId=users.Id
comments.PostId=posts.Id
comments.UserId=users.Id
postLinks.PostId=posts.Id
postLinks.RelatedPostId=posts.Id
badges.UserId=users.Id

    【Question】
    What are the post history type IDs for post ID 3720 and how many unique users have commented on the post?

    【Evidence】
    

    Please read and understand the database schema carefully, and generate an executable SQL based on the user's question and evidence. 

SQL: SELECT T1.PostHistoryTypeId, (SELECT COUNT(DISTINCT UserId) FROM comments WHERE PostId = 3720) AS NumberOfUsers FROM postHistory AS T1 WHERE T1.PostId = 3720