• Places
    • Home
    • Graphs
    • Prefixes
  • Admin
    • Users
    • Settings
    • Plugins
    • Statistics
  • CPACK
    • Home
    • List packs
    • Submit pack
  • Repository
    • Load local file
    • Load from HTTP
    • Load from library
    • Remove triples
    • Clear repository
  • Query
    • YASGUI SPARQL Editor
    • Simple Form
    • SWISH Prolog shell
  • Help
    • Documentation
    • Tutorial
    • Roadmap
    • HTTP Services
  • Login

1.1 Warnings from CQL
All Application Manual Name SummaryHelp

  • Documentation
    • Reference manual
    • Packages
      • Constraint Query Language A high level interface to SQL databases
        • library(cql/cql): CQL - Constraint Query Language
          • Warnings from CQL
            • CQL Comparisons with NULL
            • Avoid setof/3 and bagof/3 in CQL queries

1.1.1 CQL Comparisons with NULL

CQLv2 correctly compiles equality comparisons with NULL into the appropriate expression at runtime. In CQLv1, executing

A={null}, {[A], foo :: [a-A]}

would never succeed, regardless of the value of foo.a. This is no longer the case: If A is {null} then this will execute as SELECT .... WHERE a IS NULL and if A is not {null}, it will execute as SELECT .... WHERE a = ?

See the section Removing null comparisions for the dealing with the common requirement to ignore comparisons with null.

ClioPatria (version V3.1.1-51-ga0b30a5)