With SQL databases, we can use a [model][model] or an existing question as the basis for a new query, or as a common table expression [CTE][CTE].
With SQL databases, we can use a [model][model] or an existing question as the basis for a new query, or as a common table expression [CTE][cte].
For example, let's say we have a lot of data spread across a number of tables, but people are most interested in a subset of that data. We can perform a complicated query once to return those results, and save that question as a model, which people can refer to in their queries just like they would with any other table.
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@@ -37,14 +37,21 @@ FROM gizmo_orders
When this query is run, the `{% raw %}{{#5-gizmo-orders-in-2019}}{% endraw %}` tag will be substituted with the SQL query of the referenced question, surrounded by parentheses. So it'll look like this under the hood:
```
WITH gizmo_orders AS (SELECT *
FROM orders AS o
INNER JOIN products AS p
ON o.product_id = p.id
WHERE p.category = 'Gizmo'
AND o.created_at BETWEEN '2019-01-01' AND '2019-12-31')
SELECT count(*)
FROM gizmo_orders
WITH
gizmo_orders AS (
SELECT
*
FROM
orders AS o
INNER JOIN products AS p ON o.product_id = p.id
WHERE
p.category = 'Gizmo'
AND o.created_at BETWEEN '2019-01-01' AND '2019-12-31'
@@ -18,7 +18,7 @@ Field Filter, a special type of filter, have a [slightly different syntax](#fiel
This example defines a **Text** variable called `category`:
```sql
```
{% raw %}
SELECT
count(*)
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@@ -31,7 +31,7 @@ WHERE
Metabase will read the variable and attach a filter widget to the query, which people can use to change the value inserted into the `cat` variable with quotes. So if someone entered "Gizmo" into the filter widget, the query Metabase would run would be:
```sql
```
SELECT
count(*)
FROM
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@@ -118,7 +118,7 @@ Let's say you want to create a Field Filter that filters the `People` table by s
The syntax for Field Filters differs from a Text, Number, or Date variable.
```sql
```
{% raw %}
SELECT
*
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@@ -196,7 +196,7 @@ The reason is that field filters generate SQL based on the mapped field; Metabas
Your main query should be aware of all the tables that your Field Filter variable is pointing to, otherwise you'll get a SQL syntax error. For example, let's say that your main query includes a field filter like this:
```sql
```
{% raw %}
SELECT
*
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@@ -209,7 +209,7 @@ WHERE
Let's say the `{% raw %}{{ product_category }}{% endraw %}` variable refers to another question that uses the `Products` table. For the field filter to work, you'll need to include a join to `Products` in your main query.
```sql
```
{% raw %}
SELECT
*
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@@ -248,7 +248,7 @@ In the variables sidebar, you can set a default value for your variable. This va
You can also define default values directly in your query by enclosing comment syntax inside the end brackets of an optional parameter.
```sql
```
WHERE column = [[ {% raw %}{{ your_parameter }}{% endraw %} --]] your_default_value
```
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@@ -256,7 +256,7 @@ The comment will "activate" whenever you pass a value to `your_parameter`.
This is useful when defining complex default values (for example, if your default value is a function like `CURRENT_DATE`). Here's a PostgreSQL example that sets the default value of a Date filter to the current date using `CURRENT_DATE`:
```sql
```
{% raw %}
SELECT
*
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@@ -286,7 +286,7 @@ To make a clause optional in your native query, type `[[brackets around a {% raw
In this example, if no value is given to `cat`, then the query will just select all the rows from the `products` table. But if `cat` does have a value, like "Widget", then the query will only grab the products with a category type of Widget:
```sql
```
{% raw %}
SELECT
count(*)
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@@ -297,7 +297,7 @@ FROM
To use multiple optional clauses, you must include at least one regular `WHERE` clause followed by optional clauses, each starting with `AND`:
