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https://issues.apache.org/jira/browse/CALCITE-5685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17720284#comment-17720284
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ZheHu commented on CALCITE-5685:
--------------------------------
Here is a tricky point I've encountered. When parsing *SIGNED* and
{*}UNSIGNED{*}, according to
[mysql-doc|https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html#function_cast],
the former can be treated as {*}BigInt{*}, however, *UNSIGNED* values from 0
to "2^64-1", which we may not match a corresponding RelDataType(need to be
validated in CAST).
During test, I've also find two confusing issues:
# The following SQL in *function.iq* returns 2 instead of 2.00
{code:java}
select cast('2' as decimal(10, 2)) as alia;
{code}
# Testing two SQL(following SQL1 and SQL2) in JdbcTest, both the results are
beyond expectations
{code:java}
SQL1: select cast('2.1' as decimal(10, 2)) as "u";
{code}
I get: *u=2.1*, which should be *2.10*.
{code:java}
SQL2:
final String s = "select cast(\"unit_sales\" as decimal(10, 2)) as \"u\"\n"
+ "from \"sales_fact_1997\" as \"sales_fact_1997\"\n";
CalciteAssert.that()
.with(CalciteAssert.Config.FOODMART_CLONE)
.query(s)
.returnsUnordered("1.00");
{code}
The result has 4 scale, like '1.0000'.
> Support MySQL CONVERT function that works on data types
> -------------------------------------------------------
>
> Key: CALCITE-5685
> URL: https://issues.apache.org/jira/browse/CALCITE-5685
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.34.0
> Reporter: ZheHu
> Assignee: ZheHu
> Priority: Minor
>
> CONVERT function in MySQL has two usage：
> # convert(s USING transcodingName): as described in
> [CALCITE-5664|https://issues.apache.org/jira/projects/CALCITE/issues/CALCITE-5664]
> # convert(value, type): equivalent to CAST function that converts value to
> specific type.
> Here are some examples:
> * convert(150, CHAR)
> * convert(now(), DATE)
> * convert('9.5', DECIMAL(10, 2))
> * convert(15, SIGNED)
> * convert(-2, UNSIGNED)
> Noted: for CONVERT or CAST function in MySQL, they only support converting to
> some specific data
> types(binary、char、date、time、datetime、decimal、signed、unsigned. Moreover, the
> last two aren't JDBC sql Types).
>
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