An expression consists of any combination of column names, literals, operators, or functions. Follow these guidelines in combining elements to form expressions:
job_id
qualified with the table name employee
:employee.job_id
Note In some databases, terms in single quotation marks are interpreted as literal values whereas terms in double quotation marks are interpreted as database objects such as column or table references. Therefore, the Query Designer can accept terms in double quotation marks, but might interpret them differently than you expect. In SQL Server, the Query Designer always interprets double quotation marks as database object delimiters. For details, see Query Designer Considerations for SQL Server Databases.
The following table illustrates the use of expressions in a query.
Expression1 | Result |
SELECT (price * .9) |
Displays a discounted price (10% off the value in the price column). |
SELECT (lname + ', ' + fname) |
Displays the concatenated values of the last name and first name columns with a comma between them. |
SELECT sales.qty, titles.price
|
After joining two tables, sorts the result set by the total value of an order (quantity times price). |
SELECT au_lname, au_fname |
Displays authors whose area code is in the San Francisco area. |
SELECT ord_num, ord_date |
Finds all orders in the sales table that were made in the last 10 days. Today’s date is returned by the GETDATE( ) function. |
1Some of the operators and functions shown here are specific to one database. For details about what operators and functions you can use, refer to the documentation for your database.