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