resultset

Using Resultset in Java Program

由 …衆ロ難τιáo~ 提交于 2019-12-30 06:20:26
问题 Resultset rs=stmt.executeQuery("select count(*) from feedsca group by score order by score"); Using the above java code above, am retrieving the counts of rows from the table named feedsCA. While trying to retrieving the counts using rs.getInt(1),rs.getInt(2),rs.getInt(3), I end with an error saying as below, Exception in thread "main" com.microsoft.sqlserver.jdbc.SQLServerException: The result set has no current row. at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError

Convert Resultset to String array

由 孤者浪人 提交于 2019-12-30 06:17:07
问题 I need to Convert My result set to an array of Strings. I am reading Email addresses from the database and I need to be able to send them like: message.addRecipient(Message.RecipientType.CC, "abc@abc.com,abc@def.com,ghi@abc.com"); Here is My code for reading the Email addresses: import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; public class Test { public static void main(String[] args) { Connection conn = null; String iphost =

Java: Delete a selected row ResultSet, Deletes last row from the database instead?

由 橙三吉。 提交于 2019-12-29 09:09:36
问题 when I select a row and press the "remove" button: In the swing interface the selected row is removed (as expected). But In the actual database the last row is deleted whatever the selected row was (not expected). The deleted row is always the last row in the database, whatever the actual selected row was. There are no errors and no exceptions thrown in my code. it works without any interruptions. I actually added the necessary things to my code: Statement sqlStatement = conn.createStatement

Getting one value from SQL select statement in Java

由 烂漫一生 提交于 2019-12-29 07:04:52
问题 I'm trying to return a value from a select statement. Its only one value because the value I'm returning is from the primary key column. The SQL statement is SELECT itemNo FROM item WHERE itemName = 'astringvalue'; My method for getting the value looks like this: private String viewValue(Connection con, String command) throws SQLException { String value = null; Statement stmt = null; try { stmt = con.createStatement(); ResultSet rs = stmt.executeQuery(command); while (rs.next()) value = rs

Java-MySQL的JDBC连接及JDBC工具类的实现

由 安稳与你 提交于 2019-12-28 16:23:07
Java IDE 连接MySQL5.7的工具类： import java . sql . * ; /* JDBC工具类 MySQL */ public class DBHelper { //mysql private static final String DRIVER = "com.mysql.jdbc.Driver" ; //驱动类的路径 private static final String URL = "jdbc:mysql://127.0.0.1:3306/mysql?useUnicode=true&characterEncoding=UTF-8" ; private static final String USER = "root" ; private static final String PWD = "12053a1203884352" ; //获得连接 public static Connection getConn ( ) { Connection conn = null ; try { //加载驱动 Class . forName ( DRIVER ) ; //在驱动管理器的基础上获得链接 conn = DriverManager . getConnection ( URL , USER , PWD ) ; } catch (

Difference between filtering queries in JOIN and WHERE?

由 蹲街弑〆低调 提交于 2019-12-28 08:10:14
问题 In SQL I am trying to filter results based on an ID and wondering if there is any logical difference between SELECT value FROM table1 JOIN table2 ON table1.id = table2.id WHERE table1.id = 1 and SELECT value FROM table1 JOIN table2 ON table1.id = table2.id AND table1.id = 1 To me, it seems as if the logic is different though you will always get the same set of results but I wondered if there were any conditions under which you would get two different result sets (or would they always return

ResultSet: Retrieving column values by index versus retrieving by label

由 |▌冷眼眸甩不掉的悲伤 提交于 2019-12-27 23:39:50
问题 When using JDBC, I often come across constructs like ResultSet rs = ps.executeQuery(); while (rs.next()) { int id = rs.getInt(1); // Some other actions } I asked myself (and authors of code too) why not to use labels for retrieving column values: int id = rs.getInt("CUSTOMER_ID"); The best explanation I've heard is something concerning performance. But actually, does it make processing extremely fast? I don't believe so, though I have never performed measurements. Even if retrieving by label

ResultSet: Retrieving column values by index versus retrieving by label

由 我们两清 提交于 2019-12-27 23:39:28
问题 When using JDBC, I often come across constructs like ResultSet rs = ps.executeQuery(); while (rs.next()) { int id = rs.getInt(1); // Some other actions } I asked myself (and authors of code too) why not to use labels for retrieving column values: int id = rs.getInt("CUSTOMER_ID"); The best explanation I've heard is something concerning performance. But actually, does it make processing extremely fast? I don't believe so, though I have never performed measurements. Even if retrieving by label

SpringJDBC配置版的使用

由 拜拜、爱过 提交于 2019-12-27 02:41:37
数据库的连接池以c3p0为例 整体概述: 1.将c3p0的配置文件c3p0.properties放到项目的resources文件夹下 2.在spring容器(spring.xml)中将连接池加载进来 3.让spring托管连接池,即:将c3p0的配置文件中的值配置进来 4.声明springJdbc工具类,并引入连接池 5.dao层使用即可. 对于2,3,4的代码实现: spring.xml: < ? xml version = "1.0" encoding = "UTF-8" ? > < beans xmlns = "http://www.springframework.org/schema/beans" xmlns : xsi = "http://www.w3.org/2001/XMLSchema-instance" xmlns : context = "http://www.springframework.org/schema/context" xsi : schemaLocation = "http : / / www . springframework . org / schema / beans http : / / www . springframework . org / schema / beans / spring - beans . xsd http : / /

数据库连接dbcp$c3p0

由 帅比萌擦擦* 提交于 2019-12-26 05:26:24
<?xml version= "1.0" encoding= "UTF-8" ?> <c3p0-config> <!-- 这是默认配置信息 --> <default-config name= "hoobey" > <!-- 连接四大参数配置 --> <property name= "jdbcUrl" >jdbc:mysql:// localhost :3306/mydb1</property> <property name= "driverClass" >com.mysql.jdbc.Driver</property> <property name= "user" >root</property> <property name= "password" >123456</property> <!-- 池参数配置 --> <property name= "acquireIncrement" >3</property> <property name= "initialPoolSize" >10</property> <property name= "minPoolSize" >2</property> <property name= "maxPoolSize" >10</property> </default-config> </c3p0-config> package cn
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