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changes.mady.by.user Lefty Leverenz

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New Version 17

changes.mady.by.user Aihua Xu

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Code Block
languagetext
INSERT OVERWRITE TABLE target_table
  SELECT name, id, category FROM source_table_1
  UNION ALL
  SELECT name, id, "Category159" as category FROM source_table_2

Column Type Conversion 

Before HIVE-14251, Hive tries to perform implict conversion across Hive type groups. With the change of HIVE-14251, Hive will only perform implicit conversion within each type groups including string group, number group or date group, not across groups. In order to union the types from different groups such as a string type and a date type, a explicit cast from string to date or from date to string is needed in the query.

Code Block
languagetext
  SELECT name, id, cast('2001-01-01' as date) d FROM source_table_1
  UNION ALL
  SELECT name, id, hiredate as d FROM source_table_2

 

Version Information

Info
titleVersion information

In Hive 0.12.0 and earlier releases, unions can only be used within a subquery such as "SELECT * FROM (select_statement UNION ALL select_statement UNION ALL ...) unionResult".

As of Hive 0.13.0, unions can also be used in a top-level query: "select_statement UNION ALL select_statement UNION ALL ...". (See HIVE-6189.)

Before Hive 1.2.0, only UNION ALL (bag union) is supported. UNION (or UNION DISTINCT) is supported since Hive 1.2.0. (See HIVE-9039.)

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