想要除個別字段外的剩餘所有字段
這是HIVE中查詢語句的一個小技巧，一個表有很多字段，我們想要除個別字段外的剩餘所有字段，全部列出來不方便且不美觀，實際上hive語句可以解決這個問題。
選擇tableName表中除了name、id、pwd之外的所有字段：
set hive.support.quoted.identifiers=None;
select `(name|id|pwd)?+.+` from tableName;
Requirement
Suppose we are having a hive partition table. This table is partitioned by the year of joining. Our requirement is to drop multiple partitions in hive.
Components Involved
- Hive
- HDFS
Sample Data
Let’s say we are having given sample data:
Here, 1 record belongs to 1 partition as we will store data partitioned by the year of joining. In actual, there will be many records for each partition.
Solution
Step 1: Create Table & Load data
If you already have a partitioned table, then skip this step else read this post for creating a table and loading data into it.
Step 2: Drop Multiple Partitions
If you see sample data, we are having 10 partitions of the year from 2005 to 2014. Let’s check the partitions in the table:
In case, you want to add multiple partitions in the table, then mention all the partitions in the query like given below:
ALTER TABLE employee ADD partition (YEAR=2005) partition (YEAR=2006) partition (YEAR=2007) partition (YEAR=2008) partition (YEAR=2009) partition (YEAR=2010) partition (YEAR=2011) partition (YEAR=2014);
Here, all the given partitions will get added to the table in a single query.
CASE I: Drop Specific Partitions
We will use this step’s command if we want to drop some specific partitions from the table. Here, we are going to drop partition 2008, 2009 and 2010 only.
ALTER TABLE db_bdpbase.Employee DROP IF EXISTS PARTITION (YEAR=2008), PARTITION(YEAR=2009), PARTITION(YEAR=2010);
Here, I have mentioned all the specific partitions separated by a comma in the query. It will drop all mentioned partitions in a single query.
CASE II: Drop Range Partition
Here, We want to drop all partition above the value of 2010. That means we have to drop the partition from the value 2011 to 2014.
First, check all available partitions in the table
ALTER TABLE db_bdpbase.Employee DROP IF EXISTS PARTITION(year>2010);
It will drop all partitions from 2011 to 2014.
drop the range partitions :
ALTER TABLE db_bdpbase.Employee DROP IF EXISTS PARTITION(year>2010,year<2014);
Wrapping Up
In this post, we have seen how we can add multiple partitions as well as drop multiple partitions from the hive table. We can drop multiple specific partitions as well as any range kind of partition.
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