I am using Microsoft SQL Server 2012 and I would like to run this seemingly simple query:
SELECT
FirstEvent.id AS firstEventID,
SecondEvent.id AS secondEventID,
DATEDIFF(second, FirstEvent.WndFGEnd, SecondEvent.WndFGStart) AS gap,
FirstEvent.TitleID = SecondEvent.TitleID AS titlesSameCheck
FROM VibeFGEvents AS FirstEvent
RIGHT OUTER JOIN VibeFGEvents AS SecondEvent
ON
FirstEvent.intervalMode = SecondEvent.intervalMode
AND FirstEvent.id = SecondEvent.id - 1
AND FirstEvent.logID = SecondEvent.logID
However FirstEvent.TitleID = SecondEvent.TitleID AS titlesSameCheck
in the SELECT
clause is incorrect syntax. But the SELECT Clause (Transact-SQL) documentation includes this syntax:
SELECT [ ALL | DISTINCT ]
[ TOP ( expression ) [ PERCENT ] [ WITH TIES ] ]
<select_list>
<select_list> ::=
{
*
| { table_name | view_name | table_alias }.*
| {
[ { table_name | view_name | table_alias }. ]
{ column_name | $IDENTITY | $ROWGUID }
| udt_column_name [ { . | :: } { { property_name | field_name }
| method_name ( argument [ ,...n] ) } ]
| expression
[ [ AS ] column_alias ]
}
| column_alias = expression
} [ ,...n ]
I think that means an expression is valid in the select clause and indeed the examples given include things like 1 + 2
. Looking at the documentation for expressions:
{ constant | scalar_function | [ table_name. ] column | variable
| ( expression ) | ( scalar_subquery )
| { unary_operator } expression
| expression { binary_operator } expression
| ranking_windowed_function | aggregate_windowed_function
}
boolean equality checks are valid expressions and indeed the example expression given in the = (Equals) (Transact-SQL) documentation includes one:
SELECT DepartmentID, Name
FROM HumanResources.Department
WHERE GroupName = 'Manufacturing'
albeit in the WHERE
clause not the SELECT
clause. It looks like I cannot use =
the equality operator to compare expressions in my SELECT
clause as they are being wrongly interpreted as assignment.
How do I include a Boolean equality column comparison equivalent to FirstEvent.TitleID = SecondEvent.TitleID AS titlesSameCheck
in my SELECT
clause?
Like this:
case when FirstEvent.TitleID = SecondEvent.TitleID then 1 else 0 end as titlesSameCheck