Popular Posts

  • SQL SELECT
    The SQL SELECT statement is used to select data from a SQL database table. This is usually the very first SQL command every SQL newbie learn...
  • SQL ALIASES
    SQL aliases can be used with database tables and with database table columns, depending on task you are performing. SQL column aliases are u...
  • SQL Replication
    SQL Replication term describes a group of technologies allowing information distribution and mirroring between different databases. SQL repl...
  • SQL ORDER BY
    The SQL ORDER BY clause comes in handy when you want to sort your SQL result sets by some column(s). For example if you want to select all t...
  • SQL COUNT
    The SQL COUNT aggregate function is used to count the number of rows in a database table. The SQL COUNT syntax is simple and looks like this...
  • SQL AVG
    The SQL AVG aggregate function selects the average value for certain table column. Have a look at the SQL AVG syntax: SELECT AVG(Column1) FR...
  • SQL GROUP BY
    The SQL GROUP BY statement is used along with the SQL aggregate functions like SUM to provide means of grouping the result dataset by certai...
  • SQL MAX
    The SQL MAX aggregate function allows us to select the highest (maximum) value for a certain column. The SQL MAX function syntax is very sim...
  • SQL IN
    The SQL IN clause allows you to specify discrete values in your SQL WHERE search criteria. THE SQL IN syntax looks like this: SELECT Column1...
  • SQL LIKE
    We will use the Customers table to illustrate the SQL LIKE clause usage: FirstName LastName Email DOB Phone John Smith John.Smith@yaho...

Saturday, February 28, 2009

SQL HAVING

The SQL HAVING clause is used to restrict conditionally the output of a SQL statement, by a SQL aggregate function used in your SELECT list of columns.

You can't specify criteria in a SQL WHERE clause against a column in the SELECT list for which SQL aggregate function is used. For example the following SQL statement will generate an error:


SELECT Employee, SUM (Hours)
FROM EmployeeHours
WHERE SUM (Hours) > 24
GROUP BY Employee

The SQL HAVING clause is used to do exactly this, to specify a condition for an aggregate function which is used in your query:


SELECT Employee, SUM (Hours)
FROM EmployeeHours
GROUP BY Employee
HAVING SUM (Hours) > 24

The above SQL statement will select all employees and the sum of their respective hours, as long as this sum is greater than 24. The result of the SQL HAVING clause can be seen below:

Employee Hours
John Smith 25
Tina Crown 27
Posted by at
Labels:

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)