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COPY

COPY TO

COPY TO is used to export the contents of a table to a file.

The syntax for using COPY TO is as follows:

sql
COPY tbl TO '/xxx/xxx/output.parquet' WITH (FORMAT = 'parquet');

The command starts with the keyword COPY, followed by the name of the table you want to export data from (tbl in this case).

TO specifies the file path and name to save the exported data (/xxx/xxx/output.parquet in this case).

WITH adds options such as the file FORMAT which specifies the format of the exported file. In this example, the format is Parquet; it is a columnar storage format used for big data processing. Parquet efficiently compresses and encodes columnar data for big data analytics.

COPY FROM

COPY FROM is used to import data from a file into a table.

The syntax for using COPY FROM is as follows:

sql
COPY [<db>.]<table_name>
FROM { '<path>/[<filename>]' }
[ [ WITH ]
 (
   [ FORMAT =  { parquet } ]
   [ PATTERN = '<regex_pattern>' ]
 )
]

The command starts with the keyword COPY, followed by the name of the table you want to import data into.

FORMAT specifies the file format of the imported file. In this example, the format is Parquet.

The option PATTERN allows the usage of wildcard characters like * to specify multiple input files that match a certain pattern. For example, you can use the following syntax to import all files in the directory(which must be an absolute path) "/path/to/folder" with the filename that contains parquet:

sql
COPY tbl FROM '/path/to/folder/' WITH (FORMAT = 'parquet', PATTERN = '.*parquet.*');

Specifically, if you only have one file to import, you can use the following syntax:

sql
COPY tbl FROM '/path/to/folder/xxx.parquet' WITH (FORMAT = 'parquet');