Question: It may seem that Google Spreadsheets only exposes the first tab (you can reorder them though) to BigQuery.

I have several tables, taking data ones from the others making several calculations already, being configured by params, in the same Spreadsheet but different tabs.

How can I read other tabs than the first one from Google Spreadsheets to BigQuery?

Answer: 
Google Bigquery can only read from the first tab. See <https://cloud.google.com/bigquery/external-data-drive>.

There is an open issue in the Issue Tracker asking for this feature, you could add a "me too" to it? <https://issuetracker.google.com/issues/35905674>. There is also a work around posted on here which may help

Alternatively, you could write something using AppScript to export the data from the sheet into a BigQuery table (this may help: <https://developers.google.com/apps-script/advanced/bigquery#load_csv_data>)
You can now specify the sheet and/or range of a Google Sheet in the new BigQuery UI which you would like to use as your federated data source.
To Quote from documentation: 

> 
> Optionally indicate which sheet and cell range in the Google Sheets
>  spreadsheet to create a table from. You can specifiy: [sheet\_title]
>  for the whole sheet, or
>  [sheet\_title]![top\_left\_cell\_id]:[bottom\_right\_cell\_id]for a
>  rectangular cell range in a sheet, such as "Sheet1!A1:B20". When this
>  is not specified, the first sheet in the spreadsheet is used.
> 
> 
> 

or You can use CLI as: 

```
{   "autodetect": false,   "sourceFormat": "GOOGLE_SHEETS",    "sourceUris": [     "https://docs.google.com/spreadsheets/d/xxxxxxxxxxxxxx"   ],   "maxBadRecords": 1,   "googleSheetsOptions":   {     "range": "test_sheet!A1:B20",     "skipLeadingRows": 0   } } 

```