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Union All

UNION ALL concatenates tables together.

For example, if you have a table for every state, you can use UNION ALL to concatenate all of them into a single table with values for the whole country.

UNION ALL WITH table1, table2, ...;

The schema of each table is carried into the unioned table; no attribute is dropped. If the initial schemas match, then the unioned table has the same exact schema. If there is an attribute in one schema that is different, then the unioned table includes it at the end of the schema.

Note: Matching attributes must have matching types. If the schemas have a matching attribute, the attribute must be the same type in each schema for them to be unioned correctly.

importantimportant Important: Changing a UNION ALL statement can result in an unintentional change to tamr_id values in the unified dataset. To avoid data loss and maintain the stability of tamr_id in mastering and categorization projects, as a best practice Tamr recommends that you explicitly set the tamr_id to a value you're sure is stable in the last transformation. See Managing Primary Keys. In addition, both the origin_source_name and origin_entity_id must exist in the datasets being unioned or you must create and populate them with strings.

UNION ALL Example

For example, you have Massachusetts and Vermont datasets containing resident information, and you want to union them.

Massachusetts.csv contains:

ID

Name

Surname

002

John

Smith

003

Sarah

Brown

004

Alex

Jones

Vermont.csv contains:

First_Name

Surname

Abby

Elliot

Ben

Anderson

Carol

Baldwin

To union these two tables together, you write a script such as:

USE Massachusetts.csv; UNION ALL WITH Vermont.csv

After the transformation runs, the new, unioned table contains:

ID

Name

Surname

First_Name

002

John

Smith

003

Sarah

Brown

004

Alex

Jones

Elliot

Abby

Anderson

Ben

Baldwin

Carol


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