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From dyozie <...@git.apache.org>
Subject [GitHub] incubator-hawq-docs pull request #85: Feature/hawq-1251
Date Wed, 11 Jan 2017 22:52:59 GMT
Github user dyozie commented on a diff in the pull request:

    https://github.com/apache/incubator-hawq-docs/pull/85#discussion_r95691137
  
    --- Diff: markdown/reference/sql/CREATE-CAST.html.md.erb ---
    @@ -0,0 +1,101 @@
    +---
    +title: CREATE CAST
    +---
    +
    +Defines a new cast.
    +
    +## <a id="topic1__section2"></a>Synopsis
    +
    +``` pre
    +CREATE CAST (sourcetype AS targettype) 
    +       WITH FUNCTION funcname (argtypes) 
    +       [AS ASSIGNMENT | AS IMPLICIT]
    +
    +CREATE CAST (sourcetype AS targettype) WITHOUT FUNCTION 
    +       [AS ASSIGNMENT | AS IMPLICIT]
    +```
    +
    +## <a id="topic1__section3"></a>Description
    +
    +`CREATE CAST` defines a new cast. A cast specifies how to perform a conversion between
two data types. For example,
    +
    +```pre
    +SELECT CAST(42 AS text);
    +```
    +
    +converts the integer constant 42 to type `text` by invoking a previously specified function,
in this `case text(int4)`. If no suitable cast has been defined, the conversion fails.
    +
    +Two types may be binary compatible, which means that they can be converted into one another
without invoking any function. This requires that corresponding values use the same internal
representation. For instance, the types `text` and `varchar` are binary compatible.
    +
    +By default, a cast can be invoked only by an explicit cast request, that is an explicit
`CAST(x AS typename)` or `x:: typename` construct.
    --- End diff --
    
    <typename>


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