Re: ResultSetMetaData precise typ information

On 21-Jul-05, at 7:45 AM, stefanlack@gmx.de wrote:

> I'm interested in retrieving the most
> precise type information as possible from PreparedStatements.
> I'm using this driver: 8.1dev-400 JDBC 3
>
> 1) ResultSetMetaData.getTableName(int column) is returning "".
> Isn't it possible to return the result of getBaseTableName(int
> column) in
> getTableName, like this
>
>     public abstract class AbstractJdbc2ResultSetMetaData  .. {
>     ..
>     public String getTableName(int column) throws SQLException
>     {
>         //return "";
>     return getBaseTableName(column);
>     }
>     ..
>     }

You're correct, does anyone know why getTableName is returning "",

when getBaseTableName is implemented ?

>
> 2)Is there a way to determine "length information" for result types in
> perpared statements?
>
> The goal is not to get the length of the actual result after
> executing the
> query, of course!
> Example:
>   String query = "SELECT a, b,c FROM table1,table2;
>   PreparedStatement stmt = getConnection().prepareStatement(query);
>   ResultSetMetaData data = stmt.getMetaData();
>
> For bit values
>   If "a" is a bit(x) column,  is it possible to retrieve the value
> of x from
> the ResultSetMetaData?
> Both "data.getScale(index)" and "data.getPrecision(index)" are
> returning
> "0", not the value expected (e.g. bit(21) -> 21)
getPrecision is defined as the number of digits to the left of the
decimal, so this should be 1
getScale is defined as the number of digits to the right, this should
be 0
>
> The same problem holds for character varying(x)
This appears to be wrong in the driver, as it is returning 0.
>
> One could use the
>   DatabaseMetaData.getTables(...) method. The retrieved ResultSet
> contains
> many usefull data,
> like
> this:
> rset.getInt("COLUMN_SIZE"),rset.getInt("DECIMAL_DIGITS"),rset.getInt
> ("CHAR_OCTET_LENGTH").
>
> But I can see no way to identify the query results' columns. In the
> example:
>   - is "a" referencing "table1" or "table2" ?
>   - In the query "Select a as b from table1;" the
> data.getColumnName(index) will return "b", so the true columnname
> is not
> available.
>   May it be possible to get a reference to the original column, or
> is this
> feature not part of of the current jdbc Specification?
>
> 3) ResultSetMetaData.isNullable(int column) returns not always
> expected
> information when used for prepared Statements
> Example:
>
>   String query = "SELECT a, b,c FROM table1 WHERE a notnull and b
> notnull
> and c notnull
>   PreparedStatement stmt = getConnection().prepareStatement(query);
>   ResultSetMetaData data = stmt.getMetaData();
>
> now,  data.isNullable(1),data.isNullable(2),data.isNullable(3) are
> returning
> 1.
> I'm aware of the fact that the column "a" is maybe nullable due to
> the table
> definition,
> but clearly in this query a,b,c can never be null values.

I'm pretty sure that isNullable(n) refers to the attribute of the
table, not the data itself.
>
>
> Thanks,
>
> Stefan Lack
>
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Dave Cramer
davec@postgresintl.com
www.postgresintl.com
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