hive alter table add column after


RESTRICT is the default, limiting column changes only to table … Refer to Hive SerDe for more information. ALTER TABLE test_change CHANGE old_name new_name STRING AFTER other_col CASCADE; Syntax: But most cases we have need change the table and partitions at same time. create table part_t (x int) partitioned by (month int); -- Create an empty partition into which you could copy data files from some other source. For example, "ALTER TABLE test_change REPLACE COLUMNS (a int, b int);" will remove column 'c' from test_change's schema. With the help of “alter” functionality, we can change the column name, add the column, drop the column, change the column name, replace the column. The CASCADE|RESTRICT clause is available in Hive 1.1.0. In addition, "alter table" is usually required prior to "alter table partition .." 1. How to modify/alter the Table? This can be done only for tables with a native SerDe (DynamicSerDe, MetadataTypedColumnsetSerDe, LazySimpleSerDe and ColumnarSerDe). -- Create an empty table and define the partitioning scheme. RESTRICT is the default, limiting column change only to table metadata.” REPLACE COLUMNS can also be used to drop columns. First, specify the name of the table in which you want to add the new column. If you want to add multiple columns to a table at once using a single ALTER TABLE statement, you use the following syntax: Hi@akhtar, You can use the alter table command to add a new column to the hive table.This command can alter your table according to your requirement as shown below. Alter/ rename the tablename. In this post, I explained the steps … HIVE-8441/HIVE-7971 provided the flexibility to alter table at partition level. Point to note. Then when you retrieve data from the table Hive sets NULL values for columns that do not exist in old data files. there is a double-column called _c1 and such columns are created by the hive itself when we moving data from one table to another. 1. Instead use ADD COLUMNS to add new columns to nested fields, or ALTER COLUMN to change the properties of a nested column. To change the contents of complex data types such as structs. So adding new columns into a table is a relatively cheap metadata-only operation as Hive does not modify the existing data files. ALTER TABLE ADD|REPLACE COLUMNS with CASCADE command changes the columns of a table's metadata, and cascades the same change to all the partition metadata. Instead use ALTER TABLE table_name ALTER COLUMN column_name DROP NOT … To relax the nullability of a column. Alter table add column Change column position using this example: 2. In the second method, the last ADD COLUMN column should actually be the first column you want to append to the table.. E.g: if you want to add count, log, status in the exact order after lastname, then the syntax would actually be:. ALTER TABLE users ADD COLUMN log VARCHAR(12) NOT NULL AFTER lastname, ADD COLUMN status INT(10) UNSIGNED NOT NULL AFTER lastname, ADD COLUMN … To address these columns we need to write it inside backticks `_c1` Finally, the ALTER command will be, ALTER TABLE CHANGE `` ; Second, specify the name of the column, its data type, and constraint if applicable. We can alter the below Table attributes. ALTER TABLE default.test_table ADD columns (column1 string,column2 string) CASCADE; From the Hive documentation: “ALTER TABLE CHANGE COLUMN with CASCADE command changes the columns of a table's metadata, and cascades the same change to all the partition metadata. Today I discovered a bug that Hive can not recognise the existing data for a newly added column to a partitioned external table. 2. insert overwrite new_table select from old_table; 3. drop old_table; 4. alter new_table rename to old_table; Also if datafiles already contain new column in some position you can. $ ALTER TABLE employee ADD COLUMNS (dept STRING COMMENT 'Department name'); We often run into some issues like HIVE-6131which is due to inconsistent column descriptors between table and partitions after alter table. Here we have the facility to alter or modify the existing attributes of the Table.