[hive] How to set variables in HIVE scripts

I'm looking for the SQL equivalent of SET varname = value in Hive QL

I know I can do something like this:

SET CURRENT_DATE = '2012-09-16';
SELECT * FROM foo WHERE day >= @CURRENT_DATE

But then I get this error:

character '@' not supported here

Have you tried using the dollar sign and brackets like this:

SELECT * 
FROM foo 
WHERE day >= '${CURRENT_DATE}';

There are multiple options to set variables in Hive.

If you're looking to set Hive variable from inside the Hive shell, you can set it using hivevar. You can set string or integer datatypes. There are no problems with them.

SET hivevar:which_date=20200808;
select ${which_date};

If you're planning to set variables from shell script and want to pass those variables into your Hive script (HQL) file, you can use --hivevar option while calling hive or beeline command.

# shell script will invoke script like this
beeline --hivevar tablename=testtable -f select.hql

-- select.hql file
select * from <dbname>.${tablename};

Two easy ways:

Using hive conf

hive> set USER_NAME='FOO';
hive> select * from foobar where NAME = '${hiveconf:USER_NAME}';

Using hive vars

On your CLI set vars and then use them in hive

set hivevar:USER_NAME='FOO';

hive> select * from foobar where NAME = '${USER_NAME}';
hive> select * from foobar where NAME = '${hivevar:USER_NAME}';

Documentation: https://cwiki.apache.org/confluence/display/Hive/LanguageManual+VariableSubstitution

Just in case someone needs to parameterize hive query via cli.

For eg:

hive_query.sql

SELECT * FROM foo WHERE day >= '${hivevar:CURRENT_DATE}'

Now execute above sql file from cli:

hive --hivevar CURRENT_DATE="2012-09-16" -f hive_query.sql

You can store the output of another query in a variable and latter you can use the same in your code:

set var=select count(*) from My_table;
${hiveconf:var};

You can export the variable in shell script export CURRENT_DATE="2012-09-16"

Then in hiveql you like SELECT * FROM foo WHERE day >= '${env:CURRENT_DATE}'

Try this method:

set t=20;
select *
from myTable
where age > '${hiveconf:t}'; 

it works well on my platform.

Most of the answers here have suggested to either use hiveconf or hivevar namespace to store the variable. And all those answers are right. However, there is one more namespace.

There are total three namespaces available for holding variables.

1. hiveconf - hive started with this, all the hive configuration is stored as part of this conf. Initially, variable substitution was not part of hive and when it got introduced, all the user-defined variables were stored as part of this as well. Which is definitely not a good idea. So two more namespaces were created.
2. hivevar: To store user variables
3. system: To store system variables.

And so if you are storing a variable as part of a query (i.e. date or product_number) you should use hivevar namespace and not hiveconf namespace.

And this is how it works.

hiveconf is still the default namespace, so if you don't provide any namespace it will store your variable in hiveconf namespace.

However, when it comes to referring a variable, it's not true. By default it refers to hivevar namespace. Confusing, right? It can become clearer with the following example.

If you do not provide namespace as mentioned below, variable var will be stored in hiveconf namespace.

set var="default_namespace";

So, to access this you need to specify hiveconf namespace

select ${hiveconf:var};

And if you do not provide namespace it will give you an error as mentioned below, reason being that by default if you try to access a variable it checks in hivevar namespace only. And in hivevar there is no variable named var

select ${var}; 

We have explicitly provided hivevar namespace

set hivevar:var="hivevar_namespace";

as we are providing the namespace this will work.

select ${hivevar:var}; 

And as default, workspace used during referring a variable is hivevar, the following will work too.

select ${var};

One thing to be mindful of is setting strings then referring back to them. You have to make sure the quotes aren't colliding.

 set start_date = '2019-01-21';
 select ${hiveconf:start_date}; 

When setting dates then referring to them in code as the strings can conflict. This wouldn't work with the start_date set above.

 '${hiveconf:start_date}'

We have to be mindful of not setting twice single or double quotes for strings when referring back to them in the query.