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there is something "missing". The SQL spec specifies `null = null` to be "unknown", where i sometimes expect "true". For MSSQL this can be configured using `SET

by salzig 7y ago

there is something "missing". The SQL spec specifies `null = null` to be "unknown", where i sometimes expect "true". For MSSQL this can be configured using `SET ANSI_NULLS { ON | OFF }`. AFAIK MySQL can't be configured. Don't know about Postgres.

hobs 7y ago
For what its worth, don't do this - pretty much all db code and practitioners expect three valued logic, not two.
- salzig 7y ago
  until you have to work with a database created by an insane guy. Never needed it outside of that one project. (edit: small hint: composite primary key where parts can be null)
  - hobs 7y ago
    I have nothing to say to this but simply "I am so sorry."
quietbritishjim 7y ago
For postgres you can just use the separate operator IS NOT DISTINCT FROM to explicitly request this behaviour. In SQLite I think it's just IS. I assume most SQL databases have something similar, and that's a far better solution than applying a global config.
himinlomax 7y ago
The standard makes sense if you go back to the theoretical basis of SQL. It seems somewhat counter-intuitive only when you think of NULL as a value you set in a cell. When it's the result of a relational operation (such as a LEFT JOIN) however, the default makes sense while considering NULLs as equal to each other is typically not useful.