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copied!<p>For your first question:</p> <pre><code>SELECT A.ID, A.Name, COUNT(ab.B_ID) AS bcount FROM A LEFT JOIN A_B_Link ab ON (ab.A_ID = A.ID) GROUP BY A.ID, A.Name; </code></pre> <p>This outputs one row per row of A, with the count of matching B's. Note that you must list all columns of A in the GROUP BY statement; there's no way to use a wildcard here.</p> <p>An alternate solution is to use a correlated subquery, as @Ray Booysen shows:</p> <pre><code>SELECT A.*, (SELECT COUNT(*) FROM A_B_Link WHERE A_B_Link.A_ID = A.A_ID) AS bcount FROM A; </code></pre> <p>This works, but correlated subqueries aren't very good for performance.</p> <p>For your second question, you need something like MySQL's <code>GROUP_CONCAT()</code> aggregate function. In MySQL, you can get a comma-separated list of <code>B.Name</code> per row of A like this:</p> <pre><code>SELECT A.*, GROUP_CONCAT(B.Name) AS bname_list FROM A LEFT OUTER JOIN A_B_Link ab ON (A.ID = ab.A_ID) LEFT OUTER JOIN B ON (ab.B_ID = B.ID) GROUP BY A.ID; </code></pre> <p>There's no easy equivalent in Microsoft SQL Server. Check here for another question on SO about this: "<a href="https://stackoverflow.com/questions/451415/simulating-groupconcat-mysql-function-in-ms-sql-server-2005">Simulating group_concat MySQL function in MS SQL Server 2005?</a>"</p> <p>Or Google for '<a href="http://www.google.com/search?q=microsoft+sql+server+%22group_concat%22" rel="nofollow noreferrer">microsoft SQL server "group_concat"</a>' for a variety of other solutions.</p>

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