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FIRST and SKIP with NULL argument

FIRST and SKIP crash a Firebird 1.5.n or lower server if given a NULL argument.Fixed in 2.0.

LIKE with NULL escape

Using LIKE with a NULL escape character would crash the server.Fixed in 1.5.1.

NULLs in NOT NULL columns

NULLs can exist in NOT NULL columns in the following situations:

  • If you add a NOT NULL column to a populated table, the fields in the newly added column will all be NULL.

  • If you make an existing column NOT NULL, any NULLs already present in the column will remain in that state.

Firebird allows these NULLs to stay, also backs them up, but refuses to restore them with gbak.See [nullguide-add-not-null-field] and [nullguide-make-column-not-null].