问题
How do we alter the datatype of multiple columns in Hive ?
CREATE TABLE test_change (a int, b int, c int);
ALTER TABLE test_change CHANGE a a string b b doube c c decimal(11,2);
回答1:
As far as I know, you can't. In the Hive documentation you can find the following:
ALTER TABLE table_name [PARTITION partition_spec] CHANGE [COLUMN] col_old_name col_new_name column_type [COMMENT col_comment] [FIRST|AFTER column_name] [CASCADE|RESTRICT];
This command will allow users to change a column's name, data type, comment, or position, or an arbitrary combination of them. The PARTITION clause is available in Hive 0.14.0 and later; see Upgrading Pre-Hive 0.13.0 Decimal Columns for usage. A patch for Hive 0.13 is also available (see HIVE-7971).
The documentation is speaking about "a column". The alternative would be to write multiple queries, one for each datatype you have to change.
Reference: https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL
来源：https://stackoverflow.com/questions/41613590/alter-hive-multiple-column