Copying Data from an Internal Stage¶
Load data from your staged files into the target table.
In this Topic:
Loading Your Data¶
Execute COPY INTO <table> to load your staged data into the target table.
Loading data requires a warehouse. If you are using a warehouse that is not configured to auto resume, execute ALTER WAREHOUSE to resume the warehouse. Note that starting the warehouse could take up to five minutes.
ALTER WAREHOUSE mywarehouse RESUME;
The following example loads data from all files prefixed with
staged in your user stage using the named
my_csv_format file format created in Preparing to Load Data:
COPY INTO mytable from @~/staged FILE_FORMAT = (FORMAT_NAME = 'my_csv_format');
The following ad hoc example loads data from all files in the stage for the
mytable table. The COPY command specifies file format options instead of referencing a named file format. This example
loads CSV files with a pipe (
|) field delimiter. The COPY command skips the first line in the data files:
COPY INTO mytable FILE_FORMAT = (TYPE = CSV FIELD_DELIMITER = '|' SKIP_HEADER = 1);
Note that when copying data from files in a table stage, the FROM clause can be omitted because Snowflake automatically checks for files in the table stage.
Validating Your Data¶
Before loading your data, you can validate that the data in the uploaded files will load correctly.
To validate data in an uploaded file, execute COPY INTO <table> in validation mode using the VALIDATION_MODE parameter. The VALIDATION_MODE parameter returns any errors that it encounters in a file. You can then modify the data in the file to ensure it loads without error.
In addition, the ON_ERROR copy option for the COPY INTO <table> command indicates what action to perform if errors are encountered in a file during loading.
Monitoring Files Staged Internally¶
Snowflake maintains detailed metadata for each file uploaded into internal stage (for users, tables, and stages), including:
- File name
- File size (compressed, if compression was specified during upload)
- LAST_MODIFIED date, i.e. the timestamp when the data file was initially staged or when it was last modified, whichever is later
In addition, Snowflake retains historical data for COPY INTO commands executed within the previous 14 days. The metadata can be used to monitor and manage the loading process, including deleting files after upload completes:
- Use the LIST command to view the status of data files that have been staged.
- Monitor the status of each COPY INTO <table> command on the History page of the Snowflake web interface.
- Use the VALIDATE function to validate the data files you’ve loaded and retrieve any errors encountered during the load.
- Use the LOAD_HISTORY Information Schema view to retrieve the history of data loaded into tables using the COPY INTO command.
Managing Data Files¶
Staged files can be deleted from a Snowflake stage (user stage, table stage, or named stage) using the following methods:
- Files that were loaded successfully can be deleted from the stage during a load by specifying the PURGE copy option in the COPY INTO <table> command.
- After the load completes, use the REMOVE command to remove the files in the stage.
Removing files ensures they aren’t inadvertently loaded again. It also improves load performance, because it reduces the number of files that COPY commands must scan to verify whether existing files in a stage were loaded already.