Java SQL 查询执行，读取 ResultSet 行时出现问题

Question

我正在编写简单的 Java 代码，并且必须在我的 Postgresql 数据库上执行 SQL 查询。 这个数据库的结果（我手动检查过）是一个由一列和两个整数组成的简单表，如下所示：

我的问题是我找不到任何方法来读取这两行。 我的阅读代码是：

_conn.setReadOnly(false);

_stmt = _conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);

_stmt.setFetchSize(100);

列表 lista = new List();

_rs = _stmt.executeQuery(查询);

而 (_rs.next()) {

lista.add((short)_rs.getInt(1));

}

此代码仅读取第一行，但无法使其读取第二行。 短列表“lista”始终包含 1 个元素。 这就像如果 ResultSet 没有继续读取第二行...

如何读取这两行？

编辑：我尝试过使用 ArrayList，但它不起作用。我已经为 _conn 连接和 _stmt 语句添加了代码部分。 这是查询：

            SELECT COUNT(bffK.biological_function_feature_oid) 
        FROM biological_function_feature AS bff 
        INNER JOIN biological_function_feature_unfolded AS bffu 
        ON bff.biological_function_feature_oid = bffu.term_oid 
        INNER JOIN (    SELECT DISTINCT ON (g.gene_oid, bffu.ancestor_oid) g.gene_oid AS ance_gene, bffu.ancestor_oid AS ance_oid, mf.feature_name AS feature_name, mf.feature_id AS feature_id, ef.name AS evidence, qf.name AS qualifier  
                FROM gene2biological_function_feature AS g2bff  
                INNER JOIN biological_function_feature AS bff  
                ON g2bff.biological_function_feature_oid = bff.biological_function_feature_oid   
                INNER JOIN biological_function_feature_unfolded AS bffu  
                ON bffu.term_oid = bff.biological_function_feature_oid  
                INNER JOIN metadata.feature AS mf ON bff.feature_type = mf.feature_id   
                INNER JOIN gene AS g ON g2bff.gene_oid = g.gene_oid  
                LEFT JOIN flag.evidence_flags AS ef ON g2bff.evidence = ef.id  
                LEFT JOIN flag.qualifier_flags AS qf ON g2bff.qualifier = qf.id     
                LEFT JOIN flag.inferred_flags AS fif ON fif.id = g2bff.inferred    
                WHERE g.gene_oid=(4060969) 
                AND (bff.is_obsolete NOT IN ('t') OR bff.is_obsolete IS NULL)    
                AND (g.is_obsolete NOT IN ('t') OR g.is_obsolete IS NULL)
                AND distance=1   
                 UNION 
                SELECT DISTINCT ON (g.gene_oid, bff.biological_function_feature_oid)   
                g.gene_oid AS ance_gene, bff.biological_function_feature_oid AS ance_oid, 
                mf.feature_name AS feature_name, mf.feature_id AS feature_id,  
                ef.name AS evidence, 
                qf.name AS qualifier   
                FROM gene2biological_function_feature AS g2bff  
                INNER JOIN biological_function_feature AS bff  
                ON g2bff.biological_function_feature_oid = bff.biological_function_feature_oid    
                INNER JOIN metadata.feature AS mf ON bff.feature_type = mf.feature_id    
                INNER JOIN gene AS g ON g2bff.gene_oid = g.gene_oid  
                LEFT JOIN flag.evidence_flags AS ef ON g2bff.evidence = ef.id  
                LEFT JOIN flag.qualifier_flags AS qf ON g2bff.qualifier = qf.id     
                LEFT JOIN flag.inferred_flags AS fif ON fif.id = g2bff.inferred    
                WHERE g.gene_oid=(4060969) 
                AND (bff.is_obsolete NOT IN ('t') OR bff.is_obsolete IS NULL)   
                AND (g.is_obsolete NOT IN ('t') OR g.is_obsolete IS NULL)  
                AND ef.name NOT IN ('IEA', 'ND') 
            ) 
        AS unf ON unf.ance_oid = bffu.ancestor_oid 
        INNER JOIN gene AS gK on gk.Gene_oid=ance_gene 
        INNER JOIN biological_function_feature AS bffK 
        ON bffK.biological_function_feature_oid = bffu.ancestor_oid 
        LEFT JOIN flag.evidence_flags AS efK  
        ON evidence = efK.name 
        LEFT JOIN flag.qualifier_flags AS qfK  
        ON qualifier = qfK.name 
        WHERE bffu.distance=1 AND (bff.biological_function_feature_oid) IN (217538)
        AND evidence NOT IN ('IEA', 'ND')   
        UNION 
        SELECT COUNT(bffK.biological_function_feature_oid) 
        FROM biological_function_feature AS bff 
        INNER JOIN biological_function_feature_unfolded AS bffu 
        ON bff.biological_function_feature_oid = bffu.term_oid 
        INNER JOIN (    SELECT DISTINCT ON (g.gene_oid, bffu.ancestor_oid) g.gene_oid AS ance_gene, bffu.ancestor_oid AS ance_oid, mf.feature_name AS feature_name, mf.feature_id AS feature_id, ef.name AS evidence, qf.name AS qualifier  
                FROM gene2biological_function_feature AS g2bff  
                INNER JOIN biological_function_feature AS bff  
                ON g2bff.biological_function_feature_oid = bff.biological_function_feature_oid   
                INNER JOIN biological_function_feature_unfolded AS bffu  
                ON bffu.term_oid = bff.biological_function_feature_oid  
                INNER JOIN metadata.feature AS mf ON bff.feature_type = mf.feature_id   
                INNER JOIN gene AS g ON g2bff.gene_oid = g.gene_oid  
                LEFT JOIN flag.evidence_flags AS ef ON g2bff.evidence = ef.id  
                LEFT JOIN flag.qualifier_flags AS qf ON g2bff.qualifier = qf.id     
                LEFT JOIN flag.inferred_flags AS fif ON fif.id = g2bff.inferred    
                WHERE g.gene_oid=(4060969) 
                AND (bff.is_obsolete NOT IN ('t') OR bff.is_obsolete IS NULL)    
                AND (g.is_obsolete NOT IN ('t') OR g.is_obsolete IS NULL)
                AND distance=1   
                 UNION 
                SELECT DISTINCT ON (g.gene_oid, bff.biological_function_feature_oid)   
                g.gene_oid AS ance_gene, bff.biological_function_feature_oid AS ance_oid, 
                mf.feature_name AS feature_name, mf.feature_id AS feature_id,  
                ef.name AS evidence, 
                qf.name AS qualifier   
                FROM gene2biological_function_feature AS g2bff  
                INNER JOIN biological_function_feature AS bff  
                ON g2bff.biological_function_feature_oid = bff.biological_function_feature_oid    
                INNER JOIN metadata.feature AS mf ON bff.feature_type = mf.feature_id    
                INNER JOIN gene AS g ON g2bff.gene_oid = g.gene_oid  
                LEFT JOIN flag.evidence_flags AS ef ON g2bff.evidence = ef.id  
                LEFT JOIN flag.qualifier_flags AS qf ON g2bff.qualifier = qf.id     
                LEFT JOIN flag.inferred_flags AS fif ON fif.id = g2bff.inferred    
                WHERE g.gene_oid=(4060969) 
                AND (bff.is_obsolete NOT IN ('t') OR bff.is_obsolete IS NULL)   
                AND (g.is_obsolete NOT IN ('t') OR g.is_obsolete IS NULL)  
                AND ef.name IN ('IEA', 'ND') 
            ) 
        AS unf ON unf.ance_oid = bffu.ancestor_oid 
        INNER JOIN gene AS gK on gk.Gene_oid=ance_gene 
        INNER JOIN biological_function_feature AS bffK 
        ON bffK.biological_function_feature_oid = bffu.ancestor_oid 
        LEFT JOIN flag.evidence_flags AS efK  
        ON evidence = efK.name 
        LEFT JOIN flag.qualifier_flags AS qfK  
        ON qualifier = qfK.name 
        WHERE bffu.distance=1 AND (bff.biological_function_feature_oid) IN (217538)
        AND evidence IN ('IEA', 'ND')

Answer 1

List 是一个接口，因此您不能直接实例化，而是使用它的实现之一，如 ArrayList。另请注意，count 是 PG 中的关键字，因此请避免使用关键字作为标识符。工作解决方案：

pst = connection.prepareStatement("SELECT * FROM demo");
List<Short> lista = new ArrayList<Short>();
rs = pst.executeQuery();

while (rs.next()) {
   lista.add((short)rs.getInt(1));
}

Answer 2

List 是一个接口，尝试使用 ArrayList 之类的东西

List< Short > lista = new ArrayList< Short >();

_rs = _stmt.executeQuery(query);

     while (_rs.next()) {

lista.add((short)_rs.getShort(1));

}

Answer 3

这似乎不是语法问题。当您对数据库运行查询时，您是否也得到了一行？也许您也可以发布您的 SQL 查询。