从 JDBC 调用 Sybase Adaptive Server Enterprise 的“sp_help”

Question

为了在 Sybase ASE 中查询数据库元数据，我找到了这个相关的答案（不是公认的），非常理想：

From a Sybase Database, how I can get table description ( field names and types)?

不幸的是，我似乎找不到任何文档，我应该如何从 JDBC 调用 sp_help。根据the documentation，sp_help 返回几个游标/结果集。第一个包含有关表本身的信息，第二个包含有关列的信息等。当我这样做时：

PreparedStatement stmt = getConnection().prepareStatement("sp_help 't_language'");
ResultSet rs = stmt.executeQuery();

while (rs.next()) {
    System.out.println(rs.getObject(1));
    // ...
}

我只从第一个光标得到结果。如何访问其他的？

Answer 1

当您有多个结果集时，您需要使用execute() 方法而不是executeQuery()。 Here's an example:

CallableStatement cstmt;
ResultSet rs;
int i;
String s;
...
cstmt.execute();                        // Call the stored procedure       1 
rs = cstmt.getResultSet();              // Get the first result set        2 
while (rs.next()) {                     // Position the cursor             3 
 i = rs.getInt(1);                      // Retrieve current result set value
 System.out.println("Value from first result set = " + i);  
                                        // Print the value
}
cstmt.getMoreResults();                 // Point to the second result set  4a 
                                        // and close the first result set
rs = cstmt.getResultSet();              // Get the second result set       4b 
while (rs.next()) {                     // Position the cursor             4c 
 s = rs.getString(1);                   // Retrieve current result set value
 System.out.println("Value from second result set = " + s); 
                                        // Print the value
}
rs.close();                             // Close the result set
cstmt.close();                          // Close the statement 

Answer 2

您还需要调用 getUpdateCount() 和 getMoreResults() 来读取整个结果集。这是我用来调用 sp_helpartition 以从 SYBASE DB 检索分区信息的一些代码。

try {
    connection = getPooledConnection(poolName);
    statement = connection.createStatement();
    CallableStatement callable = connection.prepareCall(
        "{ call sp_helpartition(?) }");
    callable.setString(1,tableName);
    callable.execute();

    int partitions = 0;

    /*
     * Loop through results until there are no more result sets or
     * or update counts to read. The number of partitions is recorded
     * in the number of rows in the second result set.
     */
    for (int index = 0 ; ; index ++){
        if (callable.getMoreResults()){
            ResultSet results = callable.getResultSet();
            int count = 0 ;
            while (results.next()){
                count++;
            }
            if (index == 1){
                partitions = count;
            }
        } else if (callable.getUpdateCount() == -1){
            break ;
        }
    }
    return partitions ;
} catch (Exception e) {
    return 0 ;
} finally {
    statement.close();
    connection.close();
}

Answer 3

感谢Martin Clayton's answer here，我可以弄清楚如何在一般情况下查询 Sybase ASE 的sp_help 函数。我在blog here 中记录了有关如何完成此操作的更多详细信息。我在jOOQ 中工作了对多个 JDBC 结果集的支持。对于 sp_help，使用 jOOQ API 调用该函数可能如下所示：

Factory create = new ASEFactory(connection);

// Get a list of tables, a list of user types, etc
List<Result<Record>> tables = create.fetchMany("sp_help");

// Get some information about the my_table table, its
// columns, keys, indexes, etc
List<Result<Record>> results = create.fetchMany("sp_help 'my_table'");