Oracle SQL Developer

Retrieving Data With QueriesSee Also:■■Oracle Database Globalization Support Guide to learn about nationalcharacter setsOracle Database SQL Reference to learn about character literals6.2.3 Using a Column Alias to Change Headings When Selecting DataWhen displaying the result of a query, SQL normally uses the name of the selectedcolumn as the column heading. You can change a column heading by using a columnalias to make the heading more descriptive and easier to understand.You can specify the alias after the column name in the SELECT list using a space as aseparator. If the alias contains spaces or special characters (such as # or $), or if it iscase-sensitive, enclose the alias in double quotation marks (" ").Example 6–3 shows the use of a column alias to provide more description for eachheading of the columns selected in a query.Example 6–3Using a Column Alias-- the following retrieves the data in columns employee_id, last_name, first_name-- and provides column aliases for more descriptive headings of the columnsSELECT employee_id "Employee Id number", last_name "Employee last name",first_name "Employee first name" FROM employees;6.2.4 Restricting Data Using the WHERE ClauseThe WHERE clause uses comparison operators to identify specific rows in a table. Whenused with the SELECT statement, you can selectively retrieve rows from a table ratherthan retrieving all rows of a table.Comparison operators include those listed in Table 6–1.Table 6–1OperatorComparison OperatorsDefinition=, !=, test for equal, not equal, not equal>, >=,