The easiest way to join columns from another table into a current table is to use the Join Column wizard.
To start the Join Column wizard:
The wizard needs to know the table name from which you wish to get a column, the name of the column that you wish to join from that table into the current table, and the relation or link between the two tables. This link is made via a common domain that is used either by the tables themselves or by a column in the tables. This link or key, through which a join can be performed, should be a (common) Class or ID domain.
Short explanation of the Join Column wizard:
If you wish to create a link through the common Class or ID domain of both tables, i.e. both tables use the same domain, you will directly continue on the Output column name page.
The Aggregation method page will not appear when an aggregation is not necessary.
For more information, refer to the Join Column wizard Help.
1. Two tables which use the same domain:
The tables have a one to one relation.
You don't have to specify a key.
The link between the tables can be directly created through the domain of both tables.
2. A column in the current table uses the same domain as the second table:
The relation between the column of the current table and the second, selected table is a many to one relation.
You will need to specify a key column from the current table, i.e. key 1.
The link between the tables can then be created through the domain of the specified key column in the current table (key 1) and the domain of the second, selected table (key 2).
3. The current table uses the same domain as a column in the second table:
The relation between the records in the current table and the values in the second, selected table is possibly a one to many relation.
You will need to a key column from the second, selected table, i.e. key 2.
The link between the tables can then be created through the domain of the current table (key 1) and the domain of the specified key column in the second, selected table (key 2).
You will then thus need to specify from the second, selected table a key 2 column (the 'group by' column), an aggregation method, and optionally a weight column.
4. A column in the current table uses the same domain as a column in the second table:
The relation between the records in the current table and the second, selected table is possibly a many to many relation.
You will need to specify both a key column from the current table, i.e. key 1, as well as a key column from the second, selected table, i.e. key 2.
The link between the tables can then be created through the domain of the specified key column in the current table (key 1) and the domain of the specified key column in the second, selected table (key 2).
You will then thus need to specify from the second, selected table, a key 2 column from the second table (the 'group by' column), an aggregation method, and optionally a weight column; and from the current table a key 1 column.
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