The limit clause in Impala is employed to limit the number of rows of a resultset to a desired number, i.e., the resultset of the query doesn’t hold the records beyond the required limit.

Syntax

Following is the syntax of the Limit clause in Impala.

select * from table_name order by id limit numerical_expression;

Example

Assume we have a table named customers in the database my_db and its contents are as follows −

[quickstart.cloudera:21000] > select * from customers;

Query: select * from customers

+—-+———-+—–+———–+——–+

+—-+———-+—–+———–+——–+

| 3 | kaushik | 23 | Kota | 30000 |

| 6 | Komal | 22 | MP | 32000 |

| 1 | Ramesh | 32 | Ahmedabad | 20000 |

| 5 | Hardik | 27 | Bhopal | 40000 |

| 2 | Khilan | 25 | Delhi | 15000 |

| 8 | ram | 22 | vizag | 31000 |

| 9 | robert | 23 | banglore | 28000 |

| 7 | ram | 25 | chennai | 23000 |

| 4 | Chaitali | 25 | Mumbai | 35000 |

+—-+———-+—–+———–+——–+

Fetched 9 row(s) in 0.51s

You can arrange the records in the table in the ascending order of their id’s using the order by clause as shown below.

[quickstart.cloudera:21000] > select * from customers order by id;

Query: select * from customers order by id

+—-+———-+—–+———–+——–+

+—-+———-+—–+———–+——–+

| 1 | Ramesh | 32 | Ahmedabad | 20000 |

| 2 | Khilan | 25 | Delhi | 15000 |

| 3 | kaushik | 23 | Kota | 30000 |

| 4 | Chaitali | 25 | Mumbai | 35000 |

| 5 | Hardik | 27 | Bhopal | 40000 |

| 6 | Komal | 22 | MP | 32000 |

| 7 | ram | 25 | chennai | 23000 |

| 8 | ram | 22 | vizag | 31000 |

| 9 | robert | 23 | banglore | 28000 |

+—-+———-+—–+———–+——–+

Fetched 9 row(s) in 0.54s

Now, using the limit clause, you can restrict the number of records of the output to 4, using the limit clause as shown below.

[quickstart.cloudera:21000] > select * from customers order by id limit 4;

On executing, the above query gives the following output.

Query: select * from customers order by id limit 4

+—-+———-+—–+———–+——–+

+—-+———-+—–+———–+——–+

| 1 | Ramesh | 32 | Ahmedabad | 20000 |

| 2 | Khilan | 25 | Delhi | 15000 |

| 3 | kaushik | 23 | Kota | 30000 |

| 4 | Chaitali | 25 | Mumbai | 35000 |

+—-+———-+—–+———–+——–+

Fetched 4 row(s) in 0.64s

Impala – Offset Clause

In general, the rows within the resultset of a get query starts from 0. Using the offset clause, we will decide from where the output should be considered. for instance, if we elect the offset as 0, the result is going to be as was common and if we elect the offset as 5, the result starts from the fifth row.

impala 1

Syntax

Following is the syntax of the offsetclause in Impala.

select data from table_name Group BY col_name;

Example

Assume we have a table named customers in the database my_db and its contents are as follows −

[quickstart.cloudera:21000] > select * from customers;

Query: select * from customers

+—-+———-+—–+———–+——–+

+—-+———-+—–+———–+——–+

| 3 | kaushik | 23 | Kota | 30000 |

| 6 | Komal | 22 | MP | 32000 |

| 1 | Ramesh | 32 | Ahmedabad | 20000 |

| 5 | Hardik | 27 | Bhopal | 40000 |

| 2 | Khilan | 25 | Delhi | 15000 |

| 8 | ram | 22 | vizag | 31000 |

| 9 | robert | 23 | banglore | 28000 |

| 7 | ram | 25 | chennai | 23000 |

| 4 | Chaitali | 25 | Mumbai | 35000 |

+—-+———-+—–+———–+——–+

Fetched 9 row(s) in 0.51s

You can arrange the records in the table in the ascending order of their id’s and limit the number of records to 4, using limit and order by clauses as shown below.

Query: select * from customers order by id limit 4

+—-+———-+—–+———–+——–+

+—-+———-+—–+———–+——–+

| 1 | Ramesh | 32 | Ahmedabad | 20000 |

| 2 | Khilan | 25 | Delhi | 15000 |

| 3 | kaushik | 23 | Kota | 30000 |

| 4 | Chaitali | 25 | Mumbai | 35000 |

+—-+———-+—–+———–+——–+

Fetched 4 row(s) in 0.64s

Following is an example of the offset clause. Here, we are getting the records in the customers table in the order of their id’s and printing the first four rows starting from the 0^th row.

[quickstart.cloudera:21000] > select * from customers order by id limit 4 offset 0;

On executing, the above query gives the following result.

Query: select * from customers order by id limit 4 offset 0

+—-+———-+—–+———–+——–+

+—-+———-+—–+———–+——–+

| 1 | Ramesh | 32 | Ahmedabad | 20000 |

| 2 | Khilan | 25 | Delhi | 15000 |

| 3 | kaushik | 23 | Kota | 30000 |

| 4 | Chaitali | 25 | Mumbai | 35000 |

+—-+———-+—–+———–+——–+

Fetched 4 row(s) in 0.62s

In the same way, you can get four records from the customers table starting from the row having offset 5 as shown below.

[quickstart.cloudera:21000] > select * from customers order by id limit 4 offset 5;

Query: select * from customers order by id limit 4 offset 5

+—-+——–+—–+———-+——–+

+—-+——–+—–+———-+——–+

| 6 | Komal | 22 | MP | 32000 |

| 7 | ram | 25 | chennai | 23000 |

| 8 | ram | 22 | vizag | 31000 |

| 9 | robert | 23 | banglore | 28000 |

+—-+——–+—–+———-+——–+

Fetched 4 row(s) in 0.52s

So, this brings us to the end of blog. This Tecklearn ‘Explanation of Limit Clause and Offset Clause in Impala’ helps you with commonly asked questions if you are looking out for a job in Big Data and Hadoop Domain.

If you wish to learn Impala and build a career in Big Data or Hadoop domain, then check out our interactive, Big Data Hadoop-Architect (All in 1) Combo Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

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