System variables reference
BigQuery supports the following system variables for multi-statement queries or within sessions. You can use system variables to set or retrieve information during query execution, similar to user-defined procedural language variables.
| Name | Type | Read and write or read-only | Description |
|---|---|---|---|
@@current_job_id |
STRING |
Read-only | Job ID of the currently executing job. In the context of a multi-statement query, this returns the job responsible for the current statement, not the entire multi-statement query. |
@@dataset_id |
STRING |
Read and write |
ID of the default dataset in the current project. This ID is used when a
dataset is not specified for a project in the query. You can use the
SET statement to assign @@dataset_id to
another dataset ID in the current project. The system variables
@@dataset_project_id and @@dataset_id can be
set and used together.
|
@@dataset_project_id |
STRING |
Read and write |
ID of the default project that's used when one is not specified for a
dataset used in the query. If @@dataset_project_id is not
set, or if it is set to NULL, the query-executing project
(@@project_id) is used. You can use the SET
statement to assign @@dataset_project_id to another
project ID. The system variables @@dataset_project_id and
@@dataset_id can be set and used together.
|
@@last_job_id |
STRING |
Read-only |
Job ID of the most recent job to execute in the current
multi-statement query, not including the current one. If the
multi-statement query contains CALL statements,
this job may have originated in a different procedure.
|
@@project_id |
STRING |
Read-only |
ID of the project used to execute the current query. In the
context of a procedure, @@project_id refers to the project
that is running the multi-statement query, not the project which owns the procedure.
|
@@query_label |
STRING |
Read and write |
Query label to associate with query jobs in the current
multi-statement query or session. If set in a query, all subsequent
query jobs in the script or session will have this label.
If not set in a query, the value for this system variable is
NULL. For an example of how to set this system variable,
see
Associate jobs in a session with a label.
|
@@row_count |
INT64 |
Read-only |
If used in a multi-statement query and the previous
statement is DML, specifies the number of rows modified, inserted, or
deleted, as a result of that DML statement. If the previous statement is
a MERGE statement, @@row_count represents the combined
total number of rows inserted, removed, and deleted. This value is
NULL if not in a multi-statement query.
|
@@script.bytes_billed |
INT64 |
Read-only |
Total bytes billed so far in the currently executing
multi-statement query job. This value is NULL
if not in the job.
|
@@script.bytes_processed |
INT64 |
Read-only |
Total bytes processed so far in the currently executing
multi-statement query job. This value is NULL
if not in the job.
|
@@script.creation_time |
TIMESTAMP |
Read-only |
Creation time of the currently executing
multi-statement query job.
This value is NULL if not in the job.
|
@@script.job_id |
STRING |
Read-only |
Job ID of the currently executing
multi-statement query job. This value is
NULL if not in the job.
|
@@script.num_child_jobs |
INT64 |
Read-only |
Number of currently completed child jobs. This value is
NULL if not in the job.
|
@@script.slot_ms |
INT64 |
Read-only |
Number of slot milliseconds used so far by the script.
This value is NULL if not in the job.
|
@@session_id |
INT64 |
Read-only | ID of the session that the current query is associated with. |
@@time_zone |
STRING |
Read and write |
The default time zone to use in time zone-dependent SQL functions,
when a time zone is not specified as an argument.
@@time_zone can be modified by
using a SET statement to any valid time zone name.
At the start of each script, @@time_zone begins as
“UTC”.
|
For backward compatibility, expressions used in an OPTIONS or
FOR SYSTEM TIME AS OF clause default to the America/Los_Angeles time zone,
while all other date/time expressions default to the UTC time zone. If
@@time_zone has been set earlier in the multi-statement query, the chosen
time zone will apply to all date/time expressions, including OPTIONS and
FOR SYSTEM TIME AS OF clauses.
In addition to the system variables shown above, you can use EXCEPTION system
variables during execution of a multi-statement query. For more information
about the EXCEPTION system variables, see the procedural language statement
BEGIN...EXCEPTION.
For examples of how you can use system variables in multi-statement queries, see Set a variable.
For examples of how you can use system variables in sessions, see Example session.