Question

我按以下方式获取数据库中所有表的行数。

public Map<String,Long> getGpTableCount() throws SQLException {
    Map<String, String> gpTableMap = getScopeTableList();
    Set<String> gpTableSet = gpTableMap.keySet();       // Gets all table names
    gpCountMap = new HashMap<String, Long>();
    Iterator<String> keySetIterator_gpTables = gpTableSet.iterator();
    Connection gpAnalyticsCon = (Connection) DbManager.getGpConnection();
    while(keySetIterator_gpTables.hasNext()) {
        String gpSchemaTableName = keySetIterator_gpTables.next();  // Ex: dbname.tablename
        String[] gpparts = gpSchemaTableName.split("\\.");  // dbname, tablename
        String gpTable = gpparts[1];
        String gpCountQuery = "select '" + gpTable + "' as TableName, count(*) as Count, source_system_name from " + gpSchemaTableName + " group by source_system_name order by source_system_name";
        // resultSet(1): TableName, resultSet(2): count, resultSet(3): source_system_name
        try {
            PreparedStatement gp_pstmnt = gpAnalyticsCon.prepareStatement(gpCountQuery);
            ResultSet gpCountRs = gp_pstmnt.executeQuery();
            while(gpCountRs.next()) {
                System.out.println("Tablename: " + gpCountRs.getString(1) + " Source System Name: " + gpCountRs.getString(3) + ", Count: " + gpCountRs.getLong(2));
                gpCountMap.put(gpTable + ": " + gpCountRs.getString(3), gpCountRs.getLong(2));
            }
        } catch(SQLException e) {
            System.out.println("Table: " + gpTable + " not found on GP for the source system: ");
            e.printStackTrace();
        } catch(Exception e) {
            e.printStackTrace();
        }
    }
    gpAnalyticsCon.close();
    return gpCountMap;
}

我在这里面临的问题是，如果我想获取特定source_system_name的计数并将查询更改为String gpCountQuery = "select '" + gpTable + "' as TableName, count(*) as Count, source_system_name from " + gpSchemaTableName + " where source_system_name in ('ABCD','EFGH') group by source_system_name order by source_system_name";

对于某些表，

列中没有值＆quot; source_system_name＆＃39;我正在获取专栏＆＃34; source_system_name＆＃34;不存在例外，可以在下面看到。

Table: some_table_name not found on GP for the source system:
org.postgresql.util.PSQLException: ERROR: column "source_system_name" does not exist
  Position: 64
        at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2455)
        at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2155)
        at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:288)
        at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:430)
        at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:356)
        at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:168)
        at org.postgresql.jdbc.PgPreparedStatement.executeQuery(PgPreparedStatement.java:116)
        at com.recordcount.dao.GpHiveRecords.getGpTableCount(GpHiveRecords.java:69)

我在查询中给出了source_system_name＆＃39;＆＃39;直接条款。由于在执行查询之前没有检查，因此会导致异常。

有没有人让我知道如何在执行count查询之前在代码中添加一个条件来检查表中是否包含给定source_system_name的值，并且仅当它存在时才获取它的计数。

检查表的列值是否为null

0 个答案: