94 lines
2.9 KiB
Markdown
94 lines
2.9 KiB
Markdown
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## Getting Data with SQL
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CARTO offers a powerful SQL API for you to query and retreive data from your CARTO tables. CARTO.js offers a simple to use wrapper for sending those requests and using the results.
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### cartodb.SQL
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`cartodb.SQL` is the tool you will use to access data you store in your CARTO tables. This is a really powerful technique for returning things like: **items closest to a point**, **items ordered by date**, or **GeoJSON vector geometries**. It’s all powered with SQL and our tutorials will show you how easy it is to begin with SQL.
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##### Arguments
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Name | Description
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--- | ---
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format | should be GeoJSON.
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dp | float precision.
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jsonp | if jsonp should be used instead of CORS. This param is enabled if the browser does not support CORS.
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These arguments will be applied to all the queries performed by this object. If you want to override them for one query see **execute** options.
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##### Example
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```javascript
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var sql = new cartodb.SQL({ user: 'cartodb_user' });
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sql.execute("SELECT * FROM table_name WHERE id > {{id}}", { id: 3 })
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.done(function(data) {
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console.log(data.rows);
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})
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.error(function(errors) {
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// errors contains a list of errors
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console.log("errors:" + errors);
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})
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```
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### sql.execute(_sql [,vars][, options][, callback]_)
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It executes a sql query.
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##### Arguments
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Name |Description
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--- | ---
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sql | a string with the sql query to be executed. You can specify template variables like {{variable}} which will be filled with `vars` object.
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vars | a map with the variables to be interpolated in the sql query.
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options | accepts `format`, `dp` and `jsonp`. This object also overrides the params passed to `$.ajax`.
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##### Returns
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A promise object. You can listen for the following events:
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Events | Description
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--- | ---
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done | triggered when the data arrives.
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error | triggered when something failed.
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##### Example
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You can also use done and error methods:
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```javascript
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sql.execute('SELECT * FROM table_name')
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.done(fn)
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.error(fnError)
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```
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### sql.getBounds(_sql [,vars][, options][, callback]_)
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This query gets the bounding box for any dataset or filtered query using the CARTO.js library. The **getBounds** function is useful for guiding users to the right location on a map, or for loading the right data (at the right time), based on user actions.
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Returns the bounds `[ [sw_lat, sw_lon], [ne_lat, ne_lon ] ]` for the geometry resulting of specified query.
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##### Arguments
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Name |Description
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--- | ---
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sql | a string with the sql query to calculate the bounds from.
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##### Example
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```javascript
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sql.getBounds('select * from table').done(function(bounds) {
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console.log(bounds);
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});
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```
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#### getBounds and Leaflet
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You can use the results from `getBounds` to center data on your maps using Leaflet.
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```javascript
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sql.getBounds('select * from table').done(function(bounds) {
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map.setBounds(bounds);
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// or map.fitBounds(bounds, mapView.getSize());
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});
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```
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