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When to use the inheritance clause in PostgreSQL?
Check constraints are merged if they have the same name, and the merge will fail if their conditions are different. Table inheritance is typically established when the child table is created, using the INHERITS clause of the CREATE TABLE statement.
How does the Capitals table in PostgreSQL inherit?
In this case, the capitals table inherits all the columns of its parent table, cities. State capitals also have an extra column, state, that shows their state. In PostgreSQL, a table can inherit from zero or more other tables, and a query can reference either all rows of a table or all rows of a table plus all of its descendant tables.
Can a parent table be dropped in PostgreSQL?
Neither can columns or check constraints of child tables be dropped or altered if they are inherited from any parent tables. If you wish to remove a table and all of its descendants, one easy way is to drop the parent table with the CASCADE option (see Section 5.14 ).
How does inheritance propagate data from insert to copy?
Inheritance does not automatically propagate data from INSERT or COPY commands to other tables in the inheritance hierarchy. In our example, the following INSERT statement will fail: We might hope that the data would somehow be routed to the capitals table, but this does not happen: INSERT always inserts into exactly the table specified.
Can a table inherit from more than one parent table?
A table can inherit from more than one parent table, in which case it has the union of the columns defined by the parent tables. Any columns declared in the child table’s definition are added to these. If the same column name appears in multiple parent tables, or in both a parent table and the child’s definition,…
How are columns merged in PostgreSQL parent table?
Any columns declared in the child table’s definition are added to these. If the same column name appears in multiple parent tables, or in both a parent table and the child’s definition, then these columns are “merged” so that there is only one such column in the child table.
In this case, the capitals table inherits all the columns of its parent table, cities. State capitals also have an extra column, state, that shows their state. In PostgreSQL, a table can inherit from zero or more other tables, and a query can reference either all rows of a table or all rows of a table plus all of its descendant tables.