How to do a "NOT EXISTS"?

[Scott Royston]

I'd like to do a query like:

SELECT A.x, A.y FROM A WHERE NOT EXISTS (SELECT * FROM B WHERE B.x == A.x AND B.y == A.y)

is there any way to do this in slick?

[Stefan Zeiger]

On 2013-03-24 18:55, Scott Royston wrote:

I'd like to do a query like:

SELECT A.x, A.y FROM A WHERE NOT EXISTS (SELECT * FROM B WHERE B.x == A.x AND B.y == A.y)

for {
  a <- A if !B.filter(b => b.x === a.x && b.y === a.y).exists
} yield (a.x, a.y)

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Stefan Zeiger
Typesafe - The software stack for applications that scale
Twitter: @StefanZeiger

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[Adam Mackler]

On Wednesday, March 27, 2013 1:47:25 PM UTC-4, Stefan Zeiger wrote:

SELECT A.x, A.y FROM A WHERE NOT EXISTS (SELECT * FROM B WHERE B.x == A.x AND B.y == A.y)

for {
  a <- A if !B.filter(b => b.x === a.x && b.y === a.y).exists
} yield (a.x, a.y)

Thanks Stefan; this would be a good one to put in the documentation.  Also wondering if there shouldn't be a Query.forall() method to use for this?

--

Adam Mackler

 

 

[Naftoli Gugenheim]

Hmm, if we want to be collections-like, wouldn't it be better if it was q.exists(f) or q.filter(f).nonEmpty?

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[Christopher Vogt]

I agree. You wanna write a ticket and or open a PR :)?

Chris

On 14.12.14 06:47, Naftoli Gugenheim wrote:
> Hmm, if we want to be collections-like, wouldn't it be better if it was
> q.exists(f) or q.filter(f).nonEmpty?
>
> On Thu, Dec 11, 2014, 4:33 PM Adam Mackler <adamm...@gmail.com
> <mailto:adamm...@gmail.com>> wrote:
>
> On Wednesday, March 27, 2013 1:47:25 PM UTC-4, Stefan Zeiger wrote:
>
>> SELECT A.x, A.y FROM A WHERE NOT EXISTS (SELECT * FROM B WHERE
>> B.x == A.x AND B.y == A.y)
> for {
> a <- A if !B.filter(b => b.x === a.x && b.y === a.y).exists
> } yield (a.x, a.y)
>
>
> Thanks Stefan; this would be a good one to put in the
> documentation. Also wondering if there shouldn't be a

> *Query.forall()* method to use for this?

>
> --
> Adam Mackler
>
>
>
>
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[Wentao Zheng]

I'm trying with your solution, but it doesn't seem to compile with the following error messages

[error]  found   : slick.lifted.Rep[Boolean]

[error]  required: Boolean

[error]         user <- Users if user.id != ui.id && !Relationships.filter(_.fromUserId === ui.id).filter(_.toUserId === user.id).exists

[Naftoli Gugenheim]

Don't use !=, use =!=

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