Sql server® 2012 t-sql fundamentals

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Microsoft SQL Server 2012 T-SQL Fundamentals

The 

HAVING

 Clause

With the HAVING clause, you can specify a predicate to filter groups as opposed to filtering individual 

rows, which happens in the WHERE phase. Only groups for which the logical expression in the  HAVING 

clause evaluates to TRUE are returned by the HAVING phase to the next logical query processing 

phase. Groups for which the logical expression evaluates to FALSE or UNKNOWN are filtered out. 

Because the HAVING clause is processed after the rows have been grouped, you can refer to ag-

gregate functions in the logical expression. For example, in the query from Listing 2-1, the HAVING 

clause has the logical expression COUNT(*) > 1, meaning that the HAVING phase filters only groups 

(employee and order year) with more than one row. The following fragment of the Listing 2-1 query 

shows the steps that have been processed so far.

FROM Sales.Orders 

WHERE custid = 71 

GROUP BY empid, YEAR(orderdate)