docs/topics/impala_datatypes.xml

<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="datatypes">

  <title>Data Types</title>
  <prolog>
    <metadata>
      <data name="Category" value="Impala"/>
      <data name="Category" value="Impala Data Types"/>
      <data name="Category" value="SQL"/>
      <data name="Category" value="Data Analysts"/>
      <data name="Category" value="Developers"/>
      <data name="Category" value="SQL"/>
      <data name="Category" value="Schemas"/>
    </metadata>
  </prolog>

  <conbody>
    <p>Impala supports a set of data types that you can use for table columns,
      expression values, and function arguments and return values. </p>
    <note> Currently, Impala supports only scalar types, not composite or nested
      types. Accessing a table containing any columns with unsupported types
      causes an error. </note>
    <p outputclass="toc"/>
    <p> For the notation to write literals of each of these data types, see
        <xref href="impala_literals.xml#literals"/>. </p>
    
      <p> Impala supports a limited set of implicit casts to avoid undesired
      results from unexpected casting behavior. </p>
    <ul>
      <li> Impala does not implicitly cast between string and numeric or Boolean
        types. Always use <codeph>CAST()</codeph> for these conversions. </li>
      <li> Impala does perform implicit casts among the numeric types, when
        going from a smaller or less precise type to a larger or more precise
        one. For example, Impala will implicitly convert a
          <codeph>SMALLINT</codeph> to a <codeph>BIGINT</codeph> or
          <codeph>FLOAT</codeph>, but to convert from <codeph>DOUBLE</codeph> to
          <codeph>FLOAT</codeph> or <codeph>INT</codeph> to
          <codeph>TINYINT</codeph> requires a call to <codeph>CAST()</codeph> in
        the query. </li>
      <li> Impala does perform implicit casts from <codeph>STRING</codeph> to
          <codeph>TIMESTAMP</codeph>. Impala has a restricted set of literal
        formats for the <codeph>TIMESTAMP</codeph> data type and the
          <codeph>FROM_UNIXTIME()</codeph> format string; see <xref
          href="impala_timestamp.xml#timestamp"/> for details. </li>
    </ul>
    <p>See the topics under this section for full details on implicit and
      explicit casting for each data type, and see <xref
        href="impala_conversion_functions.xml#conversion_functions"/> for
      details about the <codeph>CAST()</codeph> function.</p>
  </conbody>
</concept>