Its in a view called APM_ComponentDetails and is stored not as a column, instead there is a column called Key, when the value is __CredentialSetId it matches the ID in the Credential table to provide what Credential is being used. and the Key value for the Windows Auth vs SQL Auth is WindowsAuthentication.
You can get them from SWQL too. The CredentialName values with NULLs are coded entries (e.g., -3 for inherited). There's a table with the other not-a-credential-ID values in the Orion SDK documentation.
SELECT aia.ApplicationID, aia.NodeID, aia.Node.Caption AS NodeName, oc.CredentialType, oc.Name AS CredentialName, aas.[VALUE] AS CredentialID FROM Orion.APM.IIS.Application aia JOIN Orion.APM.ApplicationSettings aas ON aia.ApplicationID = aas.ApplicationID LEFT JOIN Orion.Credential oc ON oc.ID = aas.[Value] WHERE aas.[KEY] = 'CredentialSetId'