如何在java中执行复合sql查询？

Posted 2023-02-24

【中文标题】如何在java中执行复合sql查询？

【英文标题】：How to execute composite sql queries in java?

【发布时间】：2011-10-10 01:05:12

【问题描述】：

如何执行以下查询并通过准备好的语句检索结果：

INSERT INTO vcVisitors (sid) VALUES (?); SELECT LAST_INSERT_ID();

有没有办法同时执行两条语句？

我已尝试执行以下操作：

Connection con = DbManager.getConnection();
PreparedStatement ps = con.PrepareStatement(
     "INSERT INTO vcVisitors (sid) VALUES (?); SELECT LAST_INSERT_ID();");
ps.setInt(1, 10);
ResultSet rs = ps.exequteQuery();
rs.next();
return rs.getInt("LAST_INSERT_ID()");

但它给了我一个错误，executeQuery 无法执行这样的查询， 我还尝试将 executeQuery 替换为以下内容：

ps.execute();
rs = ps.getResultSet();

但它给了我 SQL 语法错误：

You have an error in your SQL syntax; 
check the manual that corresponds to your mysql server version 
for the right syntax to use near 'SELECT LAST_INSERT_ID()' at line 1

但是执行查询没有问题 "INSERT INTO vcVisitors (sid) VALUES ('10'); SELECT LAST_INSERT_ID();" 直接从 mysql 控制台。

【问题讨论】：

我认为这不可能。尤其是INSERT 和SELECT。

【参考方案1】：

更新（插入）数据时使用executeUpdate 而不是executeQuery。尝试将SELECT LAST_INSERT_ID() 作为另一个查询执行。

但它不是可移植的查询。我建议改用Statement.getGeneratedKeys。请看这里：JDBC (MySQL) Retrieving AUTO_INCREMENT Column Values。

以下是正确使用 LAST_INSERT_ID() 的示例：

    Statement stmt = null;
   ResultSet rs = null;

   try 

    //
    // Create a Statement instance that we can use for
    // 'normal' result sets.

    stmt = conn.createStatement();

    //
    // Issue the DDL queries for the table for this example
    //

    stmt.executeUpdate("DROP TABLE IF EXISTS autoIncTutorial");
    stmt.executeUpdate(
            "CREATE TABLE autoIncTutorial ("
            + "priKey INT NOT NULL AUTO_INCREMENT, "
            + "dataField VARCHAR(64), PRIMARY KEY (priKey))");

    //
    // Insert one row that will generate an AUTO INCREMENT
    // key in the 'priKey' field
    //

    stmt.executeUpdate(
            "INSERT INTO autoIncTutorial (dataField) "
            + "values ('Can I Get the Auto Increment Field?')");

    //
    // Use the MySQL LAST_INSERT_ID()
    // function to do the same thing as getGeneratedKeys()
    //

    int autoIncKeyFromFunc = -1;
    rs = stmt.executeQuery("SELECT LAST_INSERT_ID()");

    if (rs.next()) 
        autoIncKeyFromFunc = rs.getInt(1);
     else 
        // throw an exception from here
    

    rs.close();

    System.out.println("Key returned from " +
                       "'SELECT LAST_INSERT_ID()': " +
                       autoIncKeyFromFunc);

 finally 

    if (rs != null) 
        try 
            rs.close();
         catch (SQLException ex) 
            // ignore
        
    

    if (stmt != null) 
        try 
            stmt.close();
         catch (SQLException ex) 
            // ignore
        
    

这里与 getGeneratedKeys 相同：

     Statement stmt = null;
   ResultSet rs = null;

   try 

    //
    // Create a Statement instance that we can use for
    // 'normal' result sets assuming you have a
    // Connection 'conn' to a MySQL database already
    // available

    stmt = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
                                java.sql.ResultSet.CONCUR_UPDATABLE);

    //
    // Issue the DDL queries for the table for this example
    //

    stmt.executeUpdate("DROP TABLE IF EXISTS autoIncTutorial");
    stmt.executeUpdate(
            "CREATE TABLE autoIncTutorial ("
            + "priKey INT NOT NULL AUTO_INCREMENT, "
            + "dataField VARCHAR(64), PRIMARY KEY (priKey))");

    //
    // Insert one row that will generate an AUTO INCREMENT
    // key in the 'priKey' field
    //

    stmt.executeUpdate(
            "INSERT INTO autoIncTutorial (dataField) "
            + "values ('Can I Get the Auto Increment Field?')",
            Statement.RETURN_GENERATED_KEYS);

    //
    // Example of using Statement.getGeneratedKeys()
    // to retrieve the value of an auto-increment
    // value
    //

    int autoIncKeyFromApi = -1;

    rs = stmt.getGeneratedKeys();

    if (rs.next()) 
        autoIncKeyFromApi = rs.getInt(1);
     else 

        // throw an exception from here
    

    rs.close();

    rs = null;

    System.out.println("Key returned from getGeneratedKeys():"
        + autoIncKeyFromApi);
 finally 

    if (rs != null) 
        try 
            rs.close();
         catch (SQLException ex) 
            // ignore
        
    

    if (stmt != null) 
        try 
            stmt.close();
         catch (SQLException ex) 
            // ignore
        
    

【讨论】：

他特别想同时执行两个查询。

【参考方案2】：

尝试：

Connection con = DbManager.getConnection();
int lastid = 0;

PreparedStatement psInsert = con.PrepareStatement(
     "INSERT INTO vcVisitors (sid) VALUES (?)");
psInsert.setInt(1, 10);
psInsert.executeUpdate();

PreparedStatement psSelect = 
    con.PrepareStatement("SELECT LAST_INSERT_ID() AS lastid");
ResultSet rs = psSelect.executeQuery();
rs.next();

lastid = rs.getInt("lastid");

rs.close();
psInsert.close();
psSelect.close();
con.close();
return lastid;

【讨论】：

是的，确实可行，但我的问题是如何一次执行多个查询

@tsds：但是两个查询总是作为两个查询运行。

【参考方案3】：

正如其他人已经说过的，这行不通。但看起来您只想获取最后插入的 ID。为此，您可以使用Statement 类的getGeneratedKeys() 方法。