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Databases SQL Reporting by Example Day 1: Joining Tables Day 1: Review

Andrew Federico
Andrew Federico
7,498 Points

Bug in quiz

https://teamtreehouse.com/library/sql-reporting-by-example/day-1-joining-tables/day-1-review

  • What does SELECT NULL = NULL; return? I wanted to point out that it will return a syntax error using the equal comparison operator. SELECT NULL ISNULL; would return NULL however. This question is incorrect.

1 Answer

Steven Parker
Steven Parker
231,184 Points

Any ordinary comparison performed on NULL will return NULL. The same is true for any math operation performed on NULL.

On the other hand, "SELECT NULL IS NULL" will return 1 (for "true").

If you're skeptical, try them out for yourself in the SQL Playground. Be aware that NULL will be displayed as an empty field there, but you can always apply the "IFNULL" function to display something else.

Andrew Federico
Andrew Federico
7,498 Points

This must be a difference between SQLite and MSSQL, as I tried it in SSMS and SELECT NULL = NULL; gave a syntax error, but SELECT NULL ISNULL; returned NULL.

Steven Parker
Steven Parker
231,184 Points

All SQL vendors do things a bit differently. The course concentrates on things that will be universal, but occasionally it may venture into areas of divergence. But any of those will be based on SQLite.