表A.

messageID / Message                     / More..
1         / This is the first message   / Etc..
2         / This is the second message  / Etc..
3         / This is the third message   / Etc..

表B

commentID / messageID / Comment 
1         / 2         / This is a comment to the second message 
2         / 2         / This is another comment to the second message 
3         / 3         / This is a comment to the third message

表之间的关系是messageID字段.

我想要一个生成这样的结果的查询,其中我从表A中提取所有字段,以及表B中每条消息的注释数计数,如下所示：

messageID  / Message                    / More...  / CommentCount
1          / This is the first message  / etc...   / 0
2          / This is the second message / etc...   / 2
3          / This is the third message  / etc...   / 1

我尝试过这样的事情：

SELECT tableA.*,count(commentID) as commentcount 
FROM tableA LEFT JOIN tableB ON tableA.messageID = tableB.messageID GROUP BY messageID

但它不起作用.有任何想法吗？似乎应该可以在一个查询中执行此操作.我正在使用MSsql.谢谢你的帮助.