Include in Select a Column That Isn't Actually in the Database

Include in SELECT a column that isn't actually in the database

You may want to use:

SELECT Name, 'Unpaid' AS Status FROM table;

The SELECT clause syntax, as defined in MSDN: SELECT Clause (Transact-SQL), is as follows:

SELECT [ ALL | DISTINCT ]
[ TOP ( expression ) [ PERCENT ] [ WITH TIES ] ] 
<select_list>

Where the expression can be a constant, function, any combination of column names, constants, and functions connected by an operator or operators, or a subquery.

Include in SELECT a column that isn't actually in the database laravel

Use DB::raw method.

Try:

select('uprn',
       'client_job_number',
       'apt_date',
       'timeslot',
       'created_at', 
       DB::raw("'00:00:00' as apt_time")
      )

Adding A Column that doesn't exist in a query

Yes, sure:

select a, b, 3 as c from table_test

That's it. It works on three db engines you've mentioned.

How to select all records from one table that do not exist in another table?

SELECT t1.name
FROM table1 t1
LEFT JOIN table2 t2 ON t2.name = t1.name
WHERE t2.name IS NULL

Q: What is happening here?

A: Conceptually, we select all rows from table1 and for each row we attempt to find a row in table2 with the same value for the name column. If there is no such row, we just leave the table2 portion of our result empty for that row. Then we constrain our selection by picking only those rows in the result where the matching row does not exist. Finally, We ignore all fields from our result except for the name column (the one we are sure that exists, from table1).

While it may not be the most performant method possible in all cases, it should work in basically every database engine ever that attempts to implement ANSI 92 SQL

How to Select Every Row Where Column Value is NOT Distinct

This is significantly faster than the EXISTS way:

SELECT [EmailAddress], [CustomerName] FROM [Customers] WHERE [EmailAddress] IN
  (SELECT [EmailAddress] FROM [Customers] GROUP BY [EmailAddress] HAVING COUNT(*) > 1)

Laravel - Add custom column in select with Eloquent query buider

Simplest would be to use DB::raw

     DB::table('modules')->get(['url', DB::raw('1 as active')]);