SQL Column Names

<h3>SQL Column Names</h3>When you specify a column name in a SQL statement, SQL can normally determine from the context which column you intend. However, if the statement involves two columns with the same name from two different tables, you must use a qualified column name to unambiguously identify the column you intend. A qualified column name specifies both the name of the table containing the column and the name of the column, separated by a period (.). For example, the column named SALES in the SALESREPS table has the qualified column name:

SALESREPS.SALES

If the column comes from a table owned by another user, a qualified table name is used in the qualified column name. For example, the BIRTHDATE column in the BIRTHDAYS table owned by the user SAM is specified by the fully qualified column name:

SAM.BIRTHDAYS.BIRTH_DATE

Qualified column names can generally be used in a SQL statement wherever a simple (unqualified) column name can appear; exceptions are noted in the descriptions of the individual SQL statements.