how do you write an sql query with a return value of httplocalhostblah plus the value of the field url_field

To write an SQL query with a return value of "http://localhost/blah/" plus the value of the field "url_field", you can use string concatenation in your query.

Here's an example of how you can do it in different databases:

MySQL:

SELECT CONCAT('http://localhost/blah/', url_field) AS full_url
FROM your_table;

PostgreSQL:

SELECT 'http://localhost/blah/' || url_field AS full_url
FROM your_table;

Oracle:

SELECT 'http://localhost/blah/' || url_field AS full_url
FROM your_table;

SQL Server:

SELECT 'http://localhost/blah/' + url_field AS full_url
FROM your_table;

Replace "your_table" with the actual name of your table, and "url_field" with the actual name of the field/column containing the URLs. The result will be a new column called "full_url" which combines the fixed string and the value of the "url_field"