How to empty a table in Esqueleto.Experimental without where_ clause

[kees Bleijenberg]

{-# TypeApplications #-}
import qualified Database.Esqueleto.Experimental as E

myHandler:: Text -> Handler Value
myHandler t = do
runDB $ E.delete $ do
v <- E.from $ E.Table @Vogel
???
retun a Value

The persistmodel for the table Vogel is
Vogel
naam     Text
deriving Show

[Jakob Schöttl]

Does that help? I asket ChatGPT ^^ I don't know Esqueleto though.

If you want to delete all the rows from a table using Esqueleto.Experimental, you can use the E.delete function without any WHERE clause. Here's an example:

haskell

import qualified Database.Esqueleto.Experimental as E

myHandler :: Handler Value
myHandler = do
    runDB $ E.delete $ E.from $ E.Table @Vogel
    return someValue

In the example above, the E.delete function is called with a query that selects all rows from the Vogel table using the E.from function. The E.Table function is used to indicate the table name explicitly. Since there is no WHERE clause, all rows in the table will be deleted.

Am 10.04.23 um 20:28 schrieb kees Bleijenberg:

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[kees Bleijenberg]

I tried your solution in this code:

myHandler :: Handler Value 

myHandler  = do 

      runDB $ E.delete $ E.from $ E.table @Vogel  -- I get a warning when I use E.Table

      return $ object [("errMsg","")]

and I got an error message about E.from:

Couldn't match type `E.SqlExpr( Entity Vogel)' with '()'

     arising from a functional dependency between:

      constraint 'Database.Esqueleto.Experimental.From.ToFrom  

          (E.From (E.SqlExpr (Entity Vogel))) ()'

          arising from a use of 'E.from'

     instance 'Database.Esqueleto.Experimental.From.ToFrom (E.From a) a'

          at <no location info>

          .......