hive wiki

Explain syntax Hive provides the explain command to display the query execution plan. Syntax: Explain [extended] Query The explain statement uses extended to provide additional information about the operation in the execution plan. This is a typical physical information, such as a file name. Hive queries are converted into sequences (this is a directed acyclic graph. These stages may be mapper/reduc

Hive has two data modification methods Load from file to hive table Hive does not perform any conversion when loading data to a table. The loading operation is a pure copy/move operation, which moves data files to the corresponding hive table. Syntax Load data [local] inpath 'filepath' [overwrite] into Table ta

Use Cases of hive concurrency Model Concurrency support (http://issues.apache.org/jira/browse/HIVE-1293) is a must for databases and Their Use Cases are well understood. At least, we should try to support concurrent reading and writing. It is useful to add several locks that are currently locked. There is no direct requirement to add an API to explicitly obtain the lock. Therefore, all locks are obtained i

Here list common operations, more refer to https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-Create%2FDrop%2FTruncateTable Simple Table Creation Create Table table_name (ID int, dtdontquery string, name string) Create a partitioned table Create Table table_name (ID int, dtdontquery string, name string) partitioned by (date string) A table can have one or more partitions. Each partition exists in a

[A "," B "," C "] 3 [D "," E "," F "] 4 [D "," E "," F "] Add a lateral view: Select mycol1, mycol2 from basetable lateral view explode (col1) mytable1 as mycol1 lateral view explode (col2) mytable2 as mycol2; The execution result is: Int mycol1 String mycol2 1 "" 1 "B" 1 "C" 2 "" 2 "B" 2 "C" 3 "D"

Union syntax Select_statement Union all select_statement... Union is used to combine the result sets of multiple select statements into an independent result set. Currently, only union all (BAG Union) is supported ). Duplicate rows are not eliminated. The number and name of columns returned by each select statement must be the same. Otherwise, a syntax error is thrown. If some extra processing is required for the Union result, the entire statement can be embedded in the from clause, as

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the MySQL syntax we use, specifically referring to the official website "DDL" and "DML", supported operators, strings, numbers, dates, and so on, built in UDF,UDAF,UDTF reference to the offical manual "Udf-wiki". UDTF we use less, but need to be very useful, such as lateral view and explode use can be used to expand the data "a lateral view example." In addition to using Udf-wiki to view

Label:Hive Architecture:is the Data warehouse infrastructure built on top of Hadoop. Similar to the database, except that the database focuses on some transactional operations, such as modify, delete, query, in the database this piece occurs more. The Data Warehouse is primarily focused on querying. For the same amount of data in the database query is relatively slow, in the Data Warehouse query efficiency is relatively fast. The Data warehouse is query-oriented, and the amount of data processed

[Root@master ~]# Hive Missing Hive execution Jar:/root/hive/hive/lib/hive-exec-*.jar Display missing hive execution Jar when running hive:/usr/h