MERGE
A
MERGE job defines a query that pulls in a set of data based on the given SELECT statement and inserts into, replaces, or deletes the data from the designated target based on the job definition. This query is then run periodically based on the RUN_INTERVAL defined within the job.Using the condition provided in the
ON clause, the query can insert records that do not meet the condition and replace those that do. Additionally, records that match the ON condition and a delete condition can be deleted.Additionally, if two jobs writing to the same table rewrite the same record, it is nondeterministic as to which job's data ends up in the table.
Note that
MERGE statements are only supported for target tables with primary key constraints.Use the MERGE command if you need to:
- Delete records
- Update based on a unique constraint
- Update data in a non-data lake table, like Snowflake or Elasticsearch
See also:
Valid identifiers match the following format:
identifier = "([^"]|"")*"|[A-Za-z_][A-Za-z0-9_]*;
{ <table_identifier>
| | {S3|REDSHIFT|SNOWFLAKE}
<catalog_name>.<schema_name>.<table_name>
}
If the
ON statement is omitted, there must be a natural join for all of the primary key and partition columns. Otherwise, there should be a column_condition for each primary key of the target table. For tables without globally unique keys, there must also be a
column_condition for each partition column. { <column_name> = <expression>
| <column_name> IN (<expression> [, ...])
| <expression> = <column_name> };
column_name must be a primary key of the target table. expression must only reference columns in the SELECT statement. The
MAP_COLUMNS_BY_NAME keyword maps columns from the SELECT statement to the table by the names of the returned columns in the query. Columns listed after EXCEPT are excluded from the final table.When using
MAP_COLUMNS_BY_NAME, the columns matched from the target and source tables in the ON condition (if not omitted) must share the same name.If a column list is provided instead of
MAP_COLUMNS_BY_NAME, it should contain all primary keys and partition columns, and their mapping should be identical to the mapping in the ON clause. If nothing is specified, fields are mapped by ordinal position in the query, and fields mapped to each special column must match exactly the
ON clause.Columns listed after the
EXCEPT keyword are not written to your target table.For example, you may have a column
to_delete; in order to use this column as your delete_condition, you need to include it within the SELECT statement. However, there is likely no meaning in having this column itself within your final target table, so using EXCEPT to_delete allows you to have it excluded from the final output.Note that since there is a selected column matching the name of the primary key column in the table we are merging into, the
ON clause here is optional.Last modified 4mo ago