> For the complete documentation index, see [llms.txt](https://docs.ngsurvey.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ngsurvey.com/form-management/security/security-items/sql-security.md).
# SQL Security
## 🔗 What is SQL Security ?
The SQL Security allows you to restrict access of the survey to a given row of an existing SQL Server table and let you reuse the data from that query for piping purposes anywhere in your survey questions or answers using the [data attributes](/form-management/security/data-attributes.md).\
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Each query can be parametrized using entries from the respondent. You can add new variables to build a user interface allowing the respondent to fill them up. These variable can then be used in your query as standard SQL parameters.
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If you want to fill a variable based on a querystring you can create a variable of type "Hidden" and pipe in its default a value from the querystring as shown below where a customer id is piped from the querystring "customerid" variable.
{% hint style="info" %}
If your user interface is composed using only hidden variable ngSurvey will automatically call the query once the survey gets loaded and no user interface will be shown.
{% endhint %}
{% hint style="warning" %}
Respondent will only be granted access if the query returns a row or if the **Access only to SQL entries** option is disabled.
{% endhint %}
Once the respondent has finished the survey and submitted his answers ngSurvey will save the retrieved SQL data along the respondent answers.
## 🔅 SQL Security properties
* **`Available Connections`** Connection that will be used to connect to your database
* **`SQL query`** SQL query or stored procedure call that will return the row and its column.
* **`Allow multiple submissions`** lets the same row submit multiple times on the same survey.
* **`Introduction message`** will be shown above the fields user interface when respondents tries to access the survey.
* **`Invalid key message`** error message shown to the user if no row is returned based on the entered value.
{% hint style="success" %}
This security item can be used as a [key provider](/form-management/security/key-provider-concepts.md).
{% endhint %}
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