# Importing data from a file to an existing table

Using the import file subcommand, you can import data from CSV or TSV files to an existing table.

Data is imported using the BulkUpsert method that provides high-efficient batch data inserts without atomicity guarantees. Data writes are split in multiple independent single-shard transactions executed in parallel. When succesfully completed, all data is guaranteed to be inserted.

In case the table already contains data, it will be replaced with imported data if the primary key matches.

The imported file must be encoded in UTF-8. Processing a line break inside a data field is not supported.

General command format:

ydb [connection options] import file csv|tsv [options]


where [connection options] are database connection options

## Subcommand parameters

### Required parameters

• -p, --path STRING: Path to the DB table.
• --input-file STRING: Path to the file in the local file system, whose data needs to be imported.

• --skip-rows NUM: Number of rows from the beginning of the file to be skipped during import. Default value: 0.
• --header: Specify this parameter if the first row (excluding the rows skipped when using the --skip-rows parameter) contains the names of data columns to be mapped to the corresponding table columns. If no header row is specified, the data will be mapped in the order of columns in the table schema.
• --delimiter STRING: Data column delimiter character. You can't specify a tab character as a delimiter in this parameter. To import a file with this delimiter, use the import file tsv subcommand. Default value: ,.
• --null-value STRING: Value to be imported as NULL. Default value: "".
• --batch-bytes VAL: Split the uploaded file into batches of the specified size. If a row does not fit into the whole batch, it will be discarded and passed in the next batch. For any size value, a batch consists of at least one row. Default value: 1 Mib.
• --max-in-flight VAL: Number of simultaneously uploaded data batches. To speed up the import of large files, you can increase the value of this parameter. Default value: 100.

## Examples

The examples use a profile named db1. For information about how to create it, see the Getting started with the YDB CLI article in the "Getting started " section.

Before running the examples, create a table series.

### Importing a file

The file contains data without additional information. The , is used as a delimiter:

1,The IT Crowd,The IT Crowd is a British sitcom.,13182
2,Silicon Valley,Silicon Valley is an American comedy television series.,16166


Note

The release_date column of the series table is of the Date type, so the release date in the imported file is represented as a number. To import values in timestamp format, use string type table columns or import them to a temporary table and then convert them to the desired type.

To import this file, run the command:

ydb import file csv -p series --input-file series.csv


As a result, the following data is imported:

┌──────────────┬───────────┬───────────────────────────────────────────────────────────┬──────────────────┐
| release_date | series_id | series_info                                               | title            |
├──────────────┼───────────┼───────────────────────────────────────────────────────────┼──────────────────┤
| "2006-02-03" | 1         | "The IT Crowd is a British sitcom."                       | "The IT Crowd"   |
├──────────────┼───────────┼───────────────────────────────────────────────────────────┼──────────────────┤
| "2014-04-06" | 2         | "Silicon Valley is an American comedy television series." | "Silicon Valley" |
└──────────────┴───────────┴───────────────────────────────────────────────────────────┴──────────────────┘


### Importing a file with the | delimiter

The file contains data without additional information. The | character is used as a delimiter:

1|IT Crowd|The IT Crowd is a British sitcom.|13182
2|Silicon Valley|Silicon Valley is an American comedy television series.|16166


To import this file, specify the --delimiter parameter set to |:

ydb import file csv -p series --input-file series.csv --delimiter "|"


### Skipping rows and counting column headers

The file contains additional information in the first and second rows and column headers in the third row. The order of data in the file rows does not correspond to the order of table columns:

#The file contains data about the series.
#
series_id,title,release_date,series_info
1,The IT Crowd,13182,The IT Crowd is a British sitcom.
2,Silicon Valley,16166,Silicon Valley is an American comedy television series.


To skip comments in the first and second rows, specify the --skip-rows 2 parameter. To process the third row as a header and map the file data to the appropriate table columns, specify the --header parameter:

ydb import file csv -p series --input-file series.csv --skip-rows 2 --header


### Replacing values with NULL

The file contains \N, a designation that is frequently used for NULL, and an empty string.

1,The IT Crowd,The IT Crowd is a British sitcom.,13182
2,Silicon Valley,"",\N
3,Lost,,\N


Specify the --null-value "\N" parameter to make sure \N is interpreted as NULL:

ydb import file csv -p series --input-file series.csv --null-value "\N"


As a result, the following data is imported:

┌──────────────┬───────────┬─────────────────────────────────────┬──────────────────┐
| release_date | series_id | series_info                         | title            |
├──────────────┼───────────┼─────────────────────────────────────┼──────────────────┤
| "2006-02-03" | 1         | "The IT Crowd is a British sitcom." | "The IT Crowd"   |
├──────────────┼───────────┼─────────────────────────────────────┼──────────────────┤
| null         | 2         | ""                                  | "Silicon Valley" |
├──────────────┼───────────┼─────────────────────────────────────┼──────────────────┤
| null         | 3         | ""                                  | "Lost"           |
└──────────────┴───────────┴─────────────────────────────────────┴──────────────────┘