Here is an example of using the boolean operator:

[Hadoop.testdomain:21000] > create table list (item string, listed boolean);
Query: create table list (item string, listed boolean)

It can be noted that the CAST() operator can be used to convert numeric values to Boolean values. A value 0 represents false and any non-zero value is converted to true. String values cannot be converted to BOOLEAN values; however, BOOLEAN values can be converted to strings, returning 1 for true and 0 for false.

Here is how Casting works with the INT data type:

Impala automatically converts the INT data type to a larger integer data type (BIGINT) or a floating-point data type (FLOAT or DOUBLE).

You can use the CAST() operator to convert INT to TINYINT, SMALLINT, STRING, or TIMESTAMP.

You can also cast an INT value to TIMESTAMP. While using Cast() with INT N to TIMESTAMP, the resulting value shows N seconds past the start of the epoch date (January 1, 1970).

Here is how Casting works with the BIGINT data type:

Impala automatically converts BIGINT to a floating-point type (FLOAT or DOUBLE).

Using the CAST() operator, BIGINT is converted to TINYINT, SMALLINT, INT, STRING, or TIMESTAMP.

Conversion of BIGINT to TIMESTAMP also works as INT. While using Cast() with BIGINT N to TIMESTAMP, the resulting value shows N seconds past the start of the epoch date (January 1, 1970).

Here is how Casting works with the SMALLINT data type:

Impala automatically converts SMALLINT to a larger integer date type (INT or BIGINT) or a floating-point type (FLOAT or DOUBLE).

Using the CAST() operator, SMALLINT is converted to TINYINT, STRING, or TIMESTAMP.

SMALLNT conversion to TIMESTAMP also works with INT. While using Cast() with SMALLINT N to TIMESTAMP, the resulting value shows N seconds past the start of the epoch date (January 1, 1970).

Here is how Casting works with the TINYINT data type:

Impala automatically converts TINYINT to a larger integer date type (SMALLINT, INT, or BIGINT) or a floating-point type (FLOAT or DOUBLE).

Using the CAST() operator, SMALLINT is converted to only STRING and TIMESTAMP.

TINYINT conversion to TIMESTAMP also works as INT. While using Cast() with BIGINT N to TIMESTAMP, the resulting value shows N seconds past the start of the epoch date (January 1, 1970).

More information on the INT data type is available in mathematical functions also.

Casting with DOUBLE works, as follows, in Impala:

Impala does not automatically convert DOUBLE to any other type.

The CAST() function can be use to convert DOUBLE values to FLOAT, TINYINT, SMALLINT, INT, BIGINT, STRING, TIMESTAMP, or BOOLEAN.

Exponential notation in DOUBLE literals can be used when casting from STRING.

As an example, value 1.0e6 represents one million.

Casting with the FLOAT data type works as follows in Impala:

Impala automatically converts FLOAT to a more precise DOUBLE value but not from DOUBLE to FLOAT.

For converting FLOAT to other data types, you can use the CAST() function and the result will be any one of the TINYINT, SMALLINT, INT, BIGINT, STRING, TIMESTAMP, or BOOLEAN data types.

Exponential notations can be use in FLOAT when needed. Exponential literals can also be used when casting from STRING; as an example 1.0e6 represents one million.

Here is how casting works with the STRING data type:

Impala does not automatically convert STRING to any other type.

The CAST() function can be used for converting STRING to other data types, such as TINYINT, SMALLINT, INT, BIGINT, FLOAT, DOUBLE, or TIMESTAMP.

Casting STRING values to BOOLEAN is not permitted; however, BOOLEAN values 1 and 0 can return as true and false, respectively.

The SUM function can be used in various ways; here are a few syntaxes using SUM:

SELECT SUM(column_name) FROM table_name;
SELECT SUM(distinct(column_name)) FROM table_name;
SELECT SUM(length(column_name)) FROM table_name;

As TIMESTAMP values are time-specific values, they are not stored using the local time zone; instead, all timestamps in Impala are stored relative to GMT.

Impala automatically converts STRING values of the correct format into TIMESTAMP values if they are written in any supported time format string.

For example, 1980-12-21 or 2001-01-01 05:05:50 can be converted to TIMESTAMP values.

Casting an integer or floating-point value N to TIMESTAMP produces a value, which is N seconds past the start of the epoch date (January 1, 1970).