Constraint

Split, Sort, Collapse: how SQL Server survives an overlapping unique update

How SQL Server shifts a whole unique column by +1 without ever creating a duplicate using Split/Sort/Collapse.

Create constraints in your datawarehouse – why and how

By Franck Pachot . We still see some developers not declaring referential integrity constraints in datawarehouse databases because they think they don't need it (integrity of data has been validated by the ETL). Here is a small demo I did(…)

Postgres unique constraint

By Franck Pachot . I'll start a series on Postgres vs. Oracle access paths because I know Oracle and I learn Postgres. While preparing it, I came upon some surprises because I'm so used to Oracle(…)

Nulls in composite keys

By Franck Pachot . Comparison of NULL can be misleading and it's even worse for unique constraint validation. Having partial nulls in a composite key can be tricky because the SQL ANSI specification is not very easy to understand, and(…)