# Run query before models and use output within models

**URL:** <https://discourse.getdbt.com/t/run-query-before-models-and-use-output-within-models/6394>\
**Category:** Help\
**Created:** [January 28, 2023, 6:01pm UTC](https://discourse.getdbt.com/t/run-query-before-models-and-use-output-within-models/6394 "2023-01-28T18:01:49Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![data\_munge](https://avatars.discourse-cdn.com/v4/letter/d/e274bd/32.png) [@data\_munge](https://discourse.getdbt.com/u/data_munge)\
**Post date:** [January 28, 2023, 6:01pm UTC](https://discourse.getdbt.com/t/run-query-before-models-and-use-output-within-models/6394/1 "2023-01-28T18:01:49Z")

</div>

### What do i want to achive?

Query existing tables to find dates (=partition) filters to be used as date (=partition) filters in dbt models. For filtering i could do joins in each and every dbt model but it turns out to execute slowly. Rather i want to find certain dates first and then substitute those dates as variables in dbt models.

### How would i like to achive this?

I would like to

1. run a query before any model exectuion. The query yields a table with a single row like: `date_1: 2020-01-01, date_2: 2020-03-1, date_3: 2020-09-01, date_4= 2020-12-01`. Store this output into variables (best dictionary) and then
2. select those values in a dbt model (e.g. in `where date_column = '{{ fetched_dates['date_1'] }}'` such that after compilation we get hardcoded values in the sql `where date_column = '2020-01-01'`

### What i tried:

I used `on_run_start` in `dbt_project.yml` to execute a macro. The macro uses `run_query` to execute a sql and store its single row output with multiple columns in a dictionary via `set fetched_dates = sql_result.rows[0]`. This seems to work. But when i reference this variable later in a dbt model as in `where date_column = '{{ fetched_dates['date_1'] }}'` it complains with `fetched_dates is undefined. This can happen when calling a macro that does not exist. Check for typos and /or install package dependencies with "dbt deps"`.

Any advice on how to proceed? Do i have to execute my date fetching query outside from dbt and then pass values to dbt as project variables? Would have much rather relied on logic within dbt itself.