Power Selecting - Order By
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The results of a query may not necessarily be returned in the desired order. Consider a query to return the first and last names from the Clients table.
SELECT LastName, FirstName from Clients;
LastName FirstName
------------------
LaBelle Nathan
Adams Gwendolyn
Smith Harold
Chavez Jose
Adams Joseph
Copland Dorothy
Johnson Diane
Smith Aaron
Franklin Susanna
Wilson Jessica
Brown Michael
Smith Josh |
The results from a query statement are returned in a seemingly arbitrary order.
One of the main advantages of a database server is its ability to sort large amounts of information quickly, so it makes sense to have the database sort the results instead of scripting a sort routine to do so. ORDER BY can be used to return sorted results.
ORDER BY accepts the columns that will act as sort indexes and then ASC for an ascending sort order or DESC for a descending sort order.
SELECT LastName, FirstName from Clients ORDER BY LastName ASC;
LastName FirstName
------------------
Adams Gwendolyn
Adams Joseph
Brown Michael
Chavez Jose
Copland Dorothy
Franklin Susanna
Johnson Diane
LaBelle Nathan
Smith Harold
Smith Aaron
Smith Josh
Wilson Jessica |
By specifying an ascending sort order based on the LastName column, results are returned alphabetically based on the client's last name.
Notice, however, a closer look reveals the entire results set is not completely alphabetical (as illustrated by the three Smiths, Harold, Aaron and Josh). Multiple sorting criteria may be specified.
SELECT LastName, FirstName from Clients ORDER BY LastName ASC, FirstName ASC;
LastName FirstName
------------------
Adams Gwendolyn
Adams Joseph
Brown Michael
Chavez Jose
Copland Dorothy
Franklin Susanna
Johnson Diane
LaBelle Nathan
Smith Aaron
Smith Harold
Smith Josh
Wilson Jessica |
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