Querying the ToolJet database is as easy as querying any other data source on ToolJet. You can use either the GUI or the SQL editor to interact with your data.
## GUI Mode
1. Go to the **Query panel**, and click on the **+Add** button to add a new query, and select **ToolJet Database**.
- **Columns**: Choose the columns, add values for the new record, and enter the values. You can also add a new column by clicking on the **+Add column** button.
The ToolJet **SQL editor** allows you to query the ToolJet Database by writing SQL queries, specifically supporting standard SQL syntax for **Data Manipulation Language (DML)** commands. This feature is only available on the [Self-Hosted](/docs/tj-setup/tj-deployment#self-hosted-tooljet) version of ToolJet.
When you are creating, updating, or deleting records in a table that has a foreign key constraint, you need to ensure that the foreign key constraint is not violated.
- If you are trying to create/update a new row in the source table, you need to ensure that the foreign key value exists in the target table. Otherwise, the operation will fail with an error message.
- Similarly, if you are trying to delete a row in the target table, you need to ensure that the foreign key value is not being referenced in the source table.
- **Selected Table**: Select the table from which you want to join the other table.
- **Type of Join**: Select the type of join you want to perform. The available options are: `Inner Join`, `Left Join`, `Right Join`, and `Full Outer Join`.
- **Joining Table**: Select the table that you want to join with the selected table. If the selected table has a foreign key relationship(s) with other tables, those tables will be listed with a foreign key icon next to their name.
- **On**: Select the column from the **selected table** and the **joining table** on which you want to join the tables. Currently, only `=` operation is supported for joining tables. If the selected table and the joining table have a foreign key relationship, both the columns will be auto-populated in the **On** dropdown.
- **AND or OR condition**: You can add multiple conditions by clicking on the **+Add more** button below each join. The conditions can be joined by `AND` or `OR` operation.
- **Filter**: Add a condition by choosing a column, an operation, and the value for filtering the records. The operations supported are same as the [filter operations](/docs/tooljet-db/database-editor#available-operations-are) for the **List rows** operation.
- **Sort**: Sort the query response by choosing a column and the order (ascending or descending).
## Mapping Date with Time Column to Table Component
The date with time column stores data in the ISO 8601 format. When querying a table with a date with time column, the column is displayed in the ISO 8601 format by default. To display the date with time column in a more readable format in the Table Component, follow these steps:
1. Connect the query to the Table Component and navigate to its properties panel.
2. In the Columns section, select the column that stores the date with time.
3. Change the column type from String to **Date Picker**.
5. In the transformation field, the `{{cellValue}}` variable contains the ISO 8601 formatted date. Convert it to a Date object using `{{new Date(cellValue)}}`, then format the Date object to meet your requirements.
In ToolJet Database, a column can be set to JSON Data Type. It can be used to store structured data like arrays or nested objects, making it useful for complex data structures such as configurations or logs. To query the JSON Data Type, follow the following steps:
### Flat JSON Object
A flat JSON object is a JSON structure where all key-value pairs exist at a single level, without any nesting. Each key is unique within the object, and all values are direct data entries rather than other objects or arrays.
1. Add **ToolJet DB** as the Data Source from the query panel.
2. Select **GUI mode** (else you can select SQL mode as well).
3. Select the **Table name**.
4. Select the desired operation from the dropdown.
5. Click on **+ Add Condition** button in front of Filter.
6. Choose column that consist JSON Data, choose the desired operation and enter the value.
7. In the input box below the column name, enter the desired key by adding `->>` before the key, example `->>city`.
A nested JSON object is a JSON structure that contains key-value pairs, where some values are themselves JSON objects or arrays. This creates a hierarchical, multi-level structure with nested layers, which can represent complex relationships between data elements.
1. Add **ToolJet DB** as the Data Source from the query panel.
2. Select **GUI mode** (else you can select SQL mode as well).
3. Select the **Table name**.
4. Select the desired operation from the dropdown.
5. Click on **+ Add Condition** button in front of Filter.
6. Choose column that consist JSON Data, choose the desired operation and enter the value.
7. In the input box below the column name, enter the desired JSON path by adding `->` before each key, example `->user->preferences->settings->notifications->sms->alerts->appointments->cancellations`.
If you have any other questions or feedback about **ToolJet Database**, please reach us out at hello@tooljet.com or join our **[Slack Community](https://join.slack.com/t/tooljet/shared_invite/zt-2rk4w42t0-ZV_KJcWU9VL1BBEjnSHLCA)**
