Add Remove Not Null Constraint From A Column as a postgres til

postgres/remove-not-null-constraint-from-a-column.md

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+# Remove Not Null Constraint From A Column
+
+When you want to add a [`not
+null`](https://www.postgresql.org/docs/current/ddl-constraints.html#id-1.5.4.6.6)
+constraint to a column, you do so by _setting_ it.
+
+```sql
+alter table books
+  alter column publication_date
+  set not null;
+```
+
+You can remove a `not null` constraint from a column, by _dropping_ it.
+
+```sql
+alter table books
+  alter column publication_date
+  drop not null;
+```
+
+Notice this excerpt of syntax from the official Postgres docs:
+
+```
+... ALTER [ COLUMN ] column_name { SET | DROP } NOT NULL
+```
+
+[source](https://www.postgresql.org/docs/current/sql-altertable.html)