> For the complete documentation index, see [llms.txt](https://ploegert.gitbook.io/til/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ploegert.gitbook.io/til/programmy/linux/is-app-installed/table-operations/truncate-tables-with-dependents.md).

# Truncate Tables With Dependents

In [Truncate All Rows](/til/programmy/linux/is-app-installed/queries/truncate-all-rows.md), I talked about how postgres's `truncate` can be used to quickly delete all rows in a table. In practice this alone won't be very useful though, because tables usually have other tables that depend on them via foreign keys. If you have tables `A` and `B` where `B` has a foreign key referencing `A`, then trying to truncate `A` will result in something like this:

```sql
> truncate A;
ERROR:  cannot truncate a table referenced in a foreign key constraint
```

Fortunately, `truncate` has some tricks up its sleeve.

If you know two tables are tied together via a foreign key constraint, you can just truncate both of them at once:

```sql
> truncate A, B;
TRUNCATE TABLE;
```

If many tables are tied together in this way and you are looking to throw all of it out, then a simpler approach is to cascade the truncation:

```sql
> truncate A cascade;
NOTICE:  truncate cascades to table "B"
TRUNCATE TABLE
```

Use these with care and potentially within transactions because your data will go bye bye.

h/t Dillon Hafer and Jack Christensen