Default Values for Columns in Big Query Tables

Default values for columns in Big Query Tables

A nullable column can (trivially) have a NULL default value, but there is no other notion of default in BigQuery (you either insert a particular value or omit the value and it will have the NULL value).

That said, if you want to wrap your raw table in a View, you can map a NULL column value to any default that you like.

How to set default value for column in Google bigquery table using API from pyhton script

Ensure you're using the latest version of the library. It was just released in version 3.4.0 a few days ago.

how to write IDENTITY(1,1) and default value in google bigquery when define a table?

BigQuery doesn't have Primary Keys, and IDENTITY is not applicable.

If you migrate data, you need to choose INT64 or STRING

BIGQUERY csv file load with an additional column with a default value

I would say you have a few choices.

1. Add a column to the CSV before uploading, e.g. with awk or preprocessing in JS.
2. Add the individual CSV files to separate tables. You can easily query across many tables as one in BigQuery. This way you can easily see what data comes from which file, and you can access table meta data for the file-name
3. Post process the data, by adding the column after the data is loaded with normal sql/api calls.
4. See also this possible duplicate How to add new column with metadata value to csv when loading it to bigquery

Google BigQuery: Add new column to a table with constant value

Seems like a solution is to use another query after the mentioned one:

UPDATE project_id.dataset.table SET A = CAST(CURRENT_TIMESTAMP() AS STRING) WHERE 1=1

How to change a column mode in Bigquery

Setting a default value is not supported, however this can be easily achieved in a query using IFNULL

For example

SELECT IFNULL(a, 0) AS field
FROM (
  SELECT 2 AS a
  UNION ALL
  SELECT NULL AS a
)

If you are loading data from external source, you could create a staging table and then run a query to generate the data for your main table using IFNULL, would need more details to give a more specific answer.

Setup Big Query table with UUID column?

BigQuery supports neither default values nor triggers. So, you have to assign these values explicitly when rows are inserted:

create table `test` (
    id string,
    x int64,
    created_at timestamp
);

INSERT INTO `test` (id, x, created_at)
    values (generate_uuid(), 1, current_timestamp);

I imagine that Google will add default values in the not-to-distant future.

Procedures in Bigquery with default parameters

You may try and consider the below possible workaround.

Since passing a NULL value on a declared parameter will result to expects 1 argument(s), 0 provided error, you may just pass an empty string and then use an IF statement to handle your desired default value if an empty string is passed.

CREATE OR REPLACE PROCEDURE `MY_DATASET.MY_PROCEDURE`(tableName STRING)
BEGIN
DECLARE table_Name STRING;
DECLARE queryString STRING;

SET table_Name = IF (tableName = '', 'MY_TABLE', tableName);

SET queryString = " SELECT * FROM MY_DATASET."||table_Name||"";

SELECT queryString;

END

Output using empty string parameter:

CALL SELECT `MY_DATASET.MY_PROCEDURE`('');

Output using a passed parameter:

CALL `MY_DATASET.MY_PROCEDURE`('TABLE_TEST');

Display default value if query results in no records in BigQuery

Option 1

Below displays row with all nulls in case if there is no result returned for your_query

#standardSQL
WITH your_query AS ( ... )
SELECT * FROM your_query 
UNION ALL 
SELECT your_query.* REPLACE ("No results found" AS result)
FROM (SELECT 1) 
LEFT JOIN your_query ON FALSE
WHERE NOT EXISTS (SELECT 1 FROM your_query)  

Row result              number  message  
1   No results found    null    null     

Option 2

If you know in advance output schema - below returns default row (assuming 0 default for number and "none" default for message

#standardSQL
WITH your_query AS ( ... )
SELECT * FROM your_query 
UNION ALL 
SELECT "No results found", 0, "none" FROM (SELECT 1) 
LEFT JOIN your_query ON FALSE
WHERE NOT EXISTS (SELECT 1 FROM your_query)

Row result              number  message  
1   No results found    0       none     

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