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This article is to share with you about the difference between Hive-sql and sql. The editor thought it was very practical, so I shared it with you as a reference. Let's follow the editor and have a look.

Differences: 1, Hive-sql does not support equivalent connections, but sql supports; 2, Hive-sql does not support "Insert into table Values ()", UPDATA, DELETE operations, but sql supports; 3, Hive-sql does not support transactions, but sql supports.

Generally speaking, hiveSQL is basically the same as SQL, and it was originally designed to enable people who can SQL but do not program MapReduce to use Hadoop for data processing.

1. Hive does not support equivalent connection.

Equivalent connections are not supported and are generally replaced by left join, right join, or inner join.

For example:

Internal associations in SQL can be written as follows: select * from a, b where a.key = b.key

This should be written in Hive: select * from a join b on a.key = b.key

You cannot use the method of omitting join in hive.

2. Semicolon character

The semicolon is the closing symbol of the sql statement, as well as in hive, but hive is not so intelligent in recognizing the semicolon and sometimes needs to escape.

3 、 NULL

In sql, null represents a null value, but in Hive, if a field of type String is an empty (empty) string, that is, the length is 0, then the result of is null judgment is False.

4. Hive does not support inserting data into existing tables or partitions

Hive only supports overwriting and rewriting the entire table.

Insert overwrite table (overwrite override)

5. Hive does not support Insert into table Values (), UPDATA, DELETE operations.

Insert into is to append data to a table or partition.

6. Hive supports embedding mapreduce programs to handle complex logic.

There are no examples to provide for the time being.

7. Hive supports writing converted data directly to different tables, as well as to partitions, hdfs and local directories.

Avoid the overhead of scanning the input table multiple times.

8. HQL does not support row-level additions, modifications, and deletions. All data is determined at the time of loading and cannot be changed.

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