SQL Alias- sql - sql tutorial - learn sql




  • Alias is a feature of SQL is supported by most or all, relational database management systems (RDBMSs).
  • Aliases will provide database administrators, as well as other database users, with the ability to lesser the amount of code required for a query & to make queries simpler to understand.
  • In addition, aliasing will be used as an obfuscation technique to protect the actual names of database fields.
  • In SQL, you can alias tables & columns.
  • A table alias is also called a correlation name.
  • A programmer can use an alias to temporarily assign another name to a table / column for the duration of a SELECT query.
  • Assigning an alias doesn’t actually rename the column / table.
  • This is often useful when either tables or their columns have very long or complex names.
  • Alias name could be anything, but usually it is kept short.
  • For eg, it might be common to use a table alias such as "pi" for a table named "price_information".
  • The general syntax of an alias is SELECT * FROM table_name [AS] alias_name.
  • Note that the AS keyword is entirely optional & is usually kept for readability purposes. Here is some sample data that the queries below will be referencing:
  • Alias refers to the practice of using a different temporary name to a database table / a column in a table.
  • The main advantage of using an alias is to help make the SQL statement more concise & readable.
  • In addition, the output of the SQL statement can become more understandable with the use of an alias.

Syntax

  • The syntax for a table alias & a column alias is as follows:
SELECT "table_alias"."column_name1" "column_alias"
FROM "table_name" "table_alias";
  • Both types of aliases are placed directly after the item they alias for, separate by a white space.

Example

  • We use the following table for our example.

Table Store_Information

Store_Name Sales Txn_Date
Los Angeles 1500 Jan-05-1999
San Diego 250 Jan-07-1999
Los Angeles 300 Jan-08-1999
Boston 700 Jan-08-1999
  • We use the same SQL query as Example 1 in the SQL GROUP BY section, except that we have put in both the column alias & the table alias:
SELECT A1.Store_Name Store, SUM(A1.Sales) "Total Sales"
FROM Store_Information A1
GROUP BY A1.Store_Name;

Notice that difference in the result:

Store Total Sales
Los Angeles 1500
Los Angeles 1800
San Diego 250
Boston 700
  • The column titles are now different.
  • That is the result of using the column alias.
  • Instead of the somewhat cryptic "Sum(Sales)", we now have "Total Sales", which is much more understandable, as the column header.
  • The advantage of using a table alias is not apparent in this example. However, they will become evident when we look at join operations in SQL.

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