Postgresql alter table used by view9/16/2023 ![]() ![]() ![]() The data files to include extra fields, or converting them to a different file format. Typically need to perform corresponding physical filesystem operations, such as rewriting Moved to different paths.) When you do an ALTER TABLE operation, you RENAME TO clause is the one exception it can cause HDFS files to be Operations do not actually rewrite, move, and so on the actual data files. Metastore database that Impala shares with Hive. In Impala, this is primarily a logical operation that updates the table metadata in the For more information, refer to the Identity Columns section.The ALTER TABLE statement changes the structure or properties of an By the use of this command, you can also "reset" the number generator. Although numbers are generated in a monotonically increasing order, it can include gaps.Starting with the number specified plus one, monotonically increasing numbers are generated for INSERT statements, which do not insert an explicit value to the identity column. When specifying the optional parameter int, the number generator will be set to this number.The contents of the table is not affected by this statement.DROP DEFAULT should be given priority over SET DEFAULT NULL.For information on the permissible expression for default value expr, refer to the Default Values section.A default value must be convertible to the data type.This statement will not change the contents of the table.If the column that is modified is a part of the distribution key (see ALTER TABLE (Distribution/Partitioning) for more information), then the table is redistributed.If you do not specify a constraint, then existing constraints are not changed. However, the only exception is when you specify a NULL constraint, a previously existing NOT NULL constraint is removed. By specifying constraints in the MODIFY command, you can only add constraints, but not modify them.For more information, refer to the Identity Columns sections. ![]() However, the data type of the modified column should be appropriate else an error is displayed.
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