Microsoft SQL Server 2012 Bible

(0 row(s) affected)Columns, Stars, Aliases, and Expressions

The title of this section may read like a bad tabloid headline, but in all seriousness it means that the SQL SELECT statement returns columns in the order in which you list them in the SELECT statement. The column may be any expression or any column in the FROM clause.

Following the FROM clause and the WHERE clause, the next logical step in the query is the list of returned expressions.

The Star

The *, commonly called “star,” is a special wildcard that includes all columns in their table order. If the query pulls from multiple tables, the * includes all columns from every table. Alternatively, tablename.* includes only the columns from the named table. Also, if you alias any tables in the FROM clause, you can return a complete column list of a specific example by using table alias.*.

Aliases

The name of the column in the underlying table becomes the name of the column in the result set. Optionally, you can change the column name using a column alias.

Expressions and constants have a blank column heading in the result set unless an alias is provided.

The AS keyword is optional, but just as with a table alias, using it is a good practice that improves the readability of the code and helps prevent errors.

To use an alias that's identical to a SQL Server keyword or that includes a space, enclose the alias in square brackets, single quotes, or double quotes. Although the square brackets are not technically required if the alias ...