Name
CAST
Synopsis
The CAST
command explicitly
converts an expression of one datatype to another.
Vendor |
Command |
---|---|
SQL Server |
Supported |
MySQL |
Not supported |
Oracle |
Not supported |
PostgreSQL |
Supported |
SQL99 Syntax and Description
CAST(expression
AS data_type[(length)])
The CAST
function converts any expression, such
as a column value or variable, into another defined datatype. The
length of the datatype may be supplied optionally for those datatypes
(such as CHAR
or VARCHAR
)
that support lengths.
Tip
Be aware that some conversions, such as DECIMAL
values to INTEGER
, result in rounding
operations. Also, some conversion operations may result in an error
if the new datatype does not have sufficient space to display the
converted value.
Example
This example retrieves the year-to-date sales as a
CHAR
and concatenates it with a literal string
and a portion of the book title. It converts
ytd_sales to CHAR(5),
plus
it shortens the length of the title to make the
results more readable:
SELECT CAST(ytd_sales AS CHAR(5)) + "Copies sold of " + CAST(title AS VARCHAR(30)) FROM titles WHERE ytd_sales IS NOT NULL AND ytd_sales > 10000 ORDER BY ytd_sales DESC
This results in the following:
--------------------------------------------------- 22246 Copies sold of The Gourmet Microwave 18722 Copies sold of You Can Combat Computer Stress 15096 Copies sold of Fifty Years in Buckingham Pala
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