BigQuery: Appending to existing table with Apps Script - google-apps-script

Question

I have a table and need to add more records based on new data from Google Sheets.
I see how I can do it with union, meaning running
Select * from (SELECT * from table),(select * from temp_table_from_sheets)
I.e: querying old table, new table. Delete old table and save the result of the query as old table.
BUT IT MUST be possible to append instead of BigQuery.Jobs.insert only.
Can you help me please?
EDIT - solution
After getting the answer below, I googled a lot and eventually came up with the following solution in Apps Script:
var sql = 'select ...'
var projectId = '...'
var datasetId = '...'
var tableId = '...'
var job = {
configuration: {
query: {
query: sql,
writeDisposition:'WRITE_APPEND',
destinationTable: {
projectId: projectId,
datasetId: datasetId,
tableId: tableId
}
}
}
};
var queryResults = BigQuery.Jobs.insert(job, projectId)

Answer 1

From BigQuery API Basics - Managing Tables:
Appending data
You can load additional data into a table either from source files or
by appending query results. Note that the schema of the loaded data
must match the schema of the existing table, but you can update the
schema before appending.
...
To append data from a query result:
Run an asynchronous query, pass in the name of your existing table,
and set writeDisposition=WRITE_APPEND.

Answer 2

Pushing Google Sheets content to BigQuery
I found it here
The tricky is sheet data to CSV.
var file = SpreadsheetApp.openByUrl(url).getSheetByName(sheetName);
// This represents ALL the data
var rows = file.getDataRange().getValues();
var rowsCSV = rows.join("\n");
var blob = Utilities.newBlob(rowsCSV, "text/csv");
var data = blob.setContentType('application/octet-stream');
// Create the data upload job.
var job = {
configuration: {
load: {
destinationTable: {
projectId: projectId,
datasetId: datasetId,
tableId: tableId
},
skipLeadingRows: 1,
writeDisposition: writeDispositionSetting
}
}
};
// send the job to BigQuery so it will run your query
var runJob = BigQuery.Jobs.insert(job, projectId, data);
Logger.log(runJob.status);
var jobId = runJob.jobReference.jobId
Logger.log('jobId: ' + jobId);
var status = BigQuery.Jobs.get(projectId, jobId);
// wait for the query to finish running before you move on
while (status.status.state === 'RUNNING') {
Utilities.sleep(500);
status = BigQuery.Jobs.get(projectId, jobId);
Logger.log('Status: ' + status);
}
Logger.log('FINNISHED!');
}