Column expressions

A column expression is a reference to a column in a table, named column_ref in the syntax of an expression.

The syntax of a list expression is as follows:

{ column_name
| table_name.column_name
| database_name.table_name.column_name
| table_name.*
}

List expressions can appear in multiple locations within an SQL statement. For example:

• In the select-list of a SELECT statement.
• In the conditions of the WHERE clause.
• In the ORDER BY clause.
• In the GROUP BY clause.
• In the VALUES clause of an INSERT statement.
• In the SET clause of an UPDATE statement.

List expressions are one of the most fundamental forms of expression in SQL statements. For example:

SELECT first_name, last_name FROM employees WHERE salary > 5000 ORDER BY last_name;

In the preceding statements, first_name, last_name, and salary are all list expressions.