Loading Default Column Values
You can optionally define a column list in your COPY command. If a column in the table is omitted from the column list, COPY will load the column with either the value supplied by the DEFAULT option that was specified in the CREATE TABLE command, or with NULL if the DEFAULT option was not specified.
If COPY attempts to assign NULL to a column that is defined as NOT NULL, the COPY command fails. For information about assigning the DEFAULT option, see CREATE TABLE.
When loading from data files on Amazon S3, the columns in the column list must be in the same order as the fields in the data file. If a field in the data file does not have a corresponding column in the column list, the COPY command fails.
When loading from Amazon DynamoDB table, order does not matter. Any fields in the Amazon DynamoDB attributes that do not match a column in the Amazon Redshift table are discarded.
The following restrictions apply when using the COPY command to load DEFAULT values into a table:
If an IDENTITY column is included in the column list, the EXPLICIT_IDS option must also be specified in the COPY command, or the COPY command will fail. Similarly, if an IDENTITY column is omitted from the column list, and the EXPLICIT_IDS option is specified, the COPY operation will fail.
Because the evaluated DEFAULT expression for a given column is the same for all loaded rows, a DEFAULT expression that uses a RANDOM() function will assign to same value to all the rows.
DEFAULT expressions that contain CURRENT_DATE or SYSDATE are set to the timestamp of the current transaction.