java.lang.NullPointerException Database.executeQuery(Unknown Source) 代码报错,找不到source,但是把SQL直接运行
在jdbc中有3种执行sql的语句分别是execute,executeQuery和executeUpdate execute执行增删改查操作 execute返回的结果是个boolean型,当返回的是...executeQuery执行查询操作 executeQuery返回的是ResultSet结果集,通常是执行了select操作。...java.sql.Statement; public class ConnDataBase { public static void main(String[] args) { execute();//增删改查 // executeQuery...catch (SQLException e) { e.printStackTrace(); } } /** * 用executeUpdate执行查询操作 */ public static void executeQuery...getConnection(); String sql = "select * from Student"; Statement st = con.createStatement(); ResultSet rs = st.executeQuery
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executeQuery executeQuery()方法是在PreparedStatement对象中执行SQL查询,并返回该查询生成的ResultSet对象, executeUpdate 该方法是在PreparedStatement
1 if (AccessCon.ExecuteSql(sql = “select * from salesData where index ='” + man....
方法一.executeQuery 用于产生单个结果集(ResultSet)的语句,例如 SELECT 语句。 被使用最多的执行 SQL 语句的方法。...//使用Connection来创建一个Statment对象 Statement stmt = conn.createStatement(); //执行查询语句 ResultSet rs =stmt.executeQuery
今天说一说execute、executeUpdate、executeQuery三者的区别(及返回值),希望能够帮助大家进步!!! 1. ...ResultSet executeQuery(String sql); 执行SQL查询,并返回ResultSet 对象。 ...execute是executeQuery和executeUpdate的综合. 使用哪一个方法由 SQL 语句所产生的内容决定。...1>方法executeQuery 用于产生单个结果集(ResultSet)的语句,例如:被执行最多的SELECT 语句。 ...但它执行SQL语句时比较麻烦,通常我们没有必要使用execute方法来执行SQL语句,而是使用executeQuery或executeUpdate更适合。
/// /// public static List ExecuteQuery.../// /// public static List ExecuteQuery.../ DataContext扩展方法 /// public static class DataContextExtends { /// /// ExecuteQuery...(this DataContext dataContext, IQueryable query) { return ExecuteQuery(dataContext..., query, 1, query.Cast().Count()); } /// /// ExecuteQuery方法扩展,代表分页的 ///
: " + e.getMessage()); } } //执行查询类的SQL语句,有返回集 public ResultSet executeQuery(String sql) { rs...stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE); rs = stmt.executeQuery...(sql); } catch(SQLException e) { System.err.println("Data.executeQuery: " + e.getMessage());...closeStmt() { try { stmt.close(); } catch(SQLException e) { System.err.println("Date.executeQuery...closeConn() { try { conn.close(); } catch(SQLException e) { System.err.println("Data.executeQuery
调用pstmt的executeUpdate()或executeQuery(),但它的方法都没有参数。...(); rs.close(); pstmt.clearParameters(); pstmt.setString(1, “S_1002”); rs = pstmt.executeQuery(); 在使用...赋值,这样就可以得到把模板变成一条完整的SQL语句,然后再调用PreparedStatement对象的executeQuery()方法获取ResultSet对象。...注意PreparedStatement对象独有的executeQuery()方法是没有参数的,而Statement的executeQuery()是需要参数(SQL语句)的。...因为在创建PreparedStatement对象时已经让它与一条SQL模板绑定在一起了,所以在调用它的executeQuery()和executeUpdate()方法时就不再需要参数了。
char *, const char *, DB::Context &, bool, DB::QueryProcessingStage::Enum, bool, DB::ReadBuffer *) executeQuery.cpp...:364 DB::executeQuery(DB::ReadBuffer&, DB::WriteBuffer&, bool, DB::Context&, std::__1::function const&, std::__1::function const&) copyData.cpp:73 DB::executeQuery...:364 DB::executeQuery(DB::ReadBuffer&, DB::WriteBuffer&, bool, DB::Context&, std::__1::function const&, std::__1::function const&) copyData.cpp:154 DB::executeQuery
executeBroadcast$1.apply(SparkPlan.scala:140) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery...produce$1.apply(WholeStageCodegenExec.scala:83) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery...produce$1.apply(WholeStageCodegenExec.scala:83) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery...produce$1.apply(WholeStageCodegenExec.scala:83) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery...$anonfun$execute$1.apply(SparkPlan.scala:127) at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery
stmt.executeUpdate("INSERT INTO user (username, password) VALUES ('init', '123456')"); ResultSet res = stmt.executeQuery...e.getMessage()); } } } stmt.executeUpdate INSERT; DELETE; UPDATE;语句都用executeUpdate函数来操作 stmt.executeQuery...SELECT;语句都用stmt.executeQuery函数来操作 ResultSet res = stmt.executeQuery;("select LAST;_INSERT_ID()"); 查询最后插入数据的...//查询数据并输出 String selectSql = "SELECT * FROM user"; ResultSet selectRes = stmt.executeQuery...Exception e) { System.out.print("MYSQL ERROR:" + e.getMessage()); } } } 查询语句使用stmt.executeQuery
"jdbc:hive://localhost:10000/default", "", ""); Statement stmt = con.createStatement(); // stmt.executeQuery...(dropSQL); // 执行删除语句 // stmt.executeQuery(createSQL); // 执行建表语句 // stmt.executeQuery(insterSQL);...// 执行插入语句 ResultSet res = stmt.executeQuery(querySQL); // 执行查询语句 while (res.next()) { System.out.println...(dropSQL); // 执行删除语句 // stmt.executeQuery(createSQL); // 执行建表语句 // stmt.executeQuery(insterSQL);...// 执行插入语句 ResultSet res = stmt.executeQuery(querySQL); // 执行查询语句 FileWriter fw = new FileWriter("/
10. execute,executeQuery,executeUpdate有什么区别?...语句executeQuery(String query)\用于执行Select查询并返回ResultSet。即使没有与查询匹配的记录,返回的ResultSet也永远不会为null。...在执行选择查询时,我们应该使用executeQuery方法,这样,如果有人尝试执行插入/更新语句,它将抛出java.sql.SQLException,并显示消息“ executeQuery方法不能用于更新...仅在不确定语句类型时,才应使用execute()方法,否则应使用executeQuery或executeUpdate方法。 Q11。您对JDBC语句了解什么?...JDBC提供了诸如execute(),executeUpdate(),executeQuery等各种方法来与数据库进行交互。
",SQL:",sql)); } // ========== 记录日志 ========== @Override public ResultSet executeQuery...(sql); } finally { doLog("executeQuery", sql, startTime); } } .......this.raw = raw; this.sql = sql; } // ========== 记录日志 ========== @Override public ResultSet executeQuery...() throws SQLException { long startTime = System.currentTimeMillis(); try { return raw.executeQuery...(); } finally { doLog("executeQuery", sql, startTime); } } ....
INSERT INTO user (username, password) VALUES ('init', '123456')"); ResultSet res = stmt.executeQuery...SELECT;语句都用stmt.executeQuery函数来操作 ResultSet res = stmt.executeQuery;(“select LAST;_INSERT_ID()”); 查询最后插入数据的...INSERT INTO user (username, password) VALUES ('init', '123456')"); ResultSet res = stmt.executeQuery...INSERT INTO user (username, password) VALUES ('init', '123456')"); ResultSet res = stmt.executeQuery...查询数据并输出 String selectSql = "SELECT * FROM user"; ResultSet selectRes = stmt.executeQuery
发送请求: mysql> SELECT * FROM system.numbers LIMIT 5; MySQLHandler 的调用栈: ->MySQLHandler::comQuery -> executeQuery...-> pipeline->execute -> MySQLOutputFormat::consume MySQLClient 接收到结果 在步骤2里,executeQuery(executeQuery.cpp...:385 DB::executeQuery(DB::ReadBuffer&, DB::WriteBuffer&, bool, DB::Context&, std::__1::function<void...:385 DB::executeQuery(DB::ReadBuffer&, DB::WriteBuffer&, bool, DB::Context&, std::__1::function<void...PipelineExecutor.cpp:764 DB::PipelineExecutor::execute(unsigned long) PipelineExecutor.cpp:479 DB::executeQuery
Statement stmt = conn.createStatement(); 4、执行SQL语句 使用Statement对象的executeQuery()或executeUpdate()方法执行SQL...executeQuery()方法用于执行SELECT语句,返回一个ResultSet对象,而executeUpdate()方法用于执行INSERT、UPDATE和DELETE语句,返回一个整数,表示受影响的行数...ResultSet rs = stmt.executeQuery("SELECT * FROM student"); 5、处理结果集 如果执行的是SELECT语句,那么需要处理返回的结果集。...Statement对象 Statement stmt = conn.createStatement(); // 执行SQL语句 ResultSet rs = stmt.executeQuery...; pstmt.setString(1, "张三"); ResultSet rs = pstmt.executeQuery();
select * from s_user where s_id='"+sname+"' and s_password='"+spass+"'"; open(); try { rs=smt.executeQuery...select * from t_user where t_id='"+tname+"' and t_password='"+tpass+"'"; open(); try { rs=smt.executeQuery...admin_user where a_id='"+aname+"' and a_password='"+apass+"'"; open(); try { rs=smt.executeQuery...new ArrayList(); String sql="select * from question"; open(); try { rs=smt.executeQuery...Model_stu>(); String sql="select * from s_user where s_id='"+s_id+"'"; open(); try { rs=smt.executeQuery
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