The Impala Query Language and Built-in Functions - Learning Cloudera Impala - page 61

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).
• TINYINT : In Impala, TINYINT represents a 1-byte integer type of data when
used with the CREATE TABLE or ALTER TABLE statement. The value of
TIYINT in Impala ranges between -128 and 127, and there is no UNSIGNED
subtype with SMALLINT .
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.
• DOUBLE : A DOUBLE data type in Impala represents an 8-byte double,
precision, floating-point data type when used with the CREATE TABLE or
ALTER TABLE statement. The value of DOUBLE in Impala ranges between
4.94065645841246544e-324d and 1.79769313486231570e+308, and this
value can either be positive or negative.
Casting with DOUBLE works, as follows, in Impala:
Impala does not automatically convert DOUBLE to any other type.