Live Queries enable a (quasi) live view on various data sources, usually [[Objects]], and renders their results inline via [[Live Preview]] either as a template, or using [[Templates]].
## Syntax
The syntax of live queries are inspired by [SQL](https://en.wikipedia.org/wiki/SQL). Below is a query that demonstrates some of the supported clauses, hover over the result and click the edit icon to shows the code that generates the view:
```query
page
order by lastModified desc
where size > 100
select name
limit 10
render [[template/page]]
```
It’s most convenient to use `/query` [[Slash Commands]] to insert a query in a page.
For those comfortable reading such things [here you can find the full query grammar](https://github.com/silverbulletmd/silverbullet/blob/main/common/markdown_parser/query.grammar).
The general syntax is to specify a `querySource` followed by a number of clauses that modify or restrict. If you haven’t already, check out how [[Objects]] work in SilverBullet.
## Clauses
## `where` [[@expression]]
A `where` clause filters out all objects that do not match a certain condition. You can have multiple `where` clauses if you like, which will have the same effect as combining them with the `and` keyword.
Here is a simple example based on a custom tag `#person` (see [[Objects]] on how this works):
```#person
name: John
age: 7
---
name: Pete
age: 25
```
To query all `person`s that are above age 21, we can use the following `where` clause:
```query
person where page = "{{@page.name}}" and age > 21
```
## `order by` [[@expression]]
In order to sort results, a `order by` clause can be used, optionally with `desc` to order in descending order (ascending is the default):
```query
person where page = "{{@page.name}}" order by age desc
```
## `limit` [[@expression]]
To limit the number of results, you can use a `limit` clause:
```query
person where page = "{{@page.name}}" limit 1
```
### `select`
To select only specific attributes from the result set, you can use the `select` clause. You can use it either simply as `select attribute1, attribute2` but also select the value of certain expressions and give them a name via the `select age + 1 as nextYear` syntax:
### `render each [[template]]` and `render all [[template]]`
$render
By default results are rendered as a table, to instead render results using [[Templates|a template]], use the `render` clause, which comes in two shapes `render each` where the template is instantiated for _each_ result (the `each` keyword is optional):
And `render all` where the entire result set is passed to the template as a list so the template can do its own iteration using `#each`, which you could then use to e.g. build a table (using this [[template/people]] template for instance):
* For scalar values this performance an equivalence tests (e.g. `10 = 10`)
* If the left operand is an array and the right operand is _not_, this will will check if the right operand is _included_ in the left operand’s value, e.g. `[1, 2, 3] = 2` will be true.
* If both operands are arrays, they will be compared for equivalence ignoring order, so this will be true: `[1, 2, 3] = [3, 2, 1]`
*`!=` the exact inverse of the meaning of `=`, e.g. `name != "Pete"`
*`<` less than, e.g. `age < 10`
*`<=` less than or equals, e.g. `age <= 10`
*`>` greater than, e.g. `age > 10`
*`>=` greater than or equals, e.g. `age >= 10`
*`=~` to match against a regular expression, e.g. `name =~ /^template\//`
*`!=~` to not match a regular expression, e.g. `name !=~ /^template\//`
*`in` member of a list (e.g. `prop in ["foo", "bar"]`)
