非常感谢,下面是我的BaseDao,貌似没有错的,你看看 package com.scce.dao; import java.io.Serializable; import java.sql.*; import javax.servlet.jsp.jstl.sql.Result; import javax.servlet.jsp.jstl.sql.ResultSupport; public class BaseDAO impleme
非常感谢,下面是我的BaseDao,貌似没有错的,你看看
package com.scce.dao;
import java.io.Serializable;
import java.sql.*;
import javax.servlet.jsp.jstl.sql.Result;
import javax.servlet.jsp.jstl.sql.ResultSupport;
public class BaseDAO implements Serializable {
private static final String DRIVER = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
private static final String URL = "jdbc:sqlserver://localhost:1433;databasename=GameCard_DB";
public static Connection getConnection() {
Connection con = null;
try {
Class.forName(DRIVER);
con = DriverManager.getConnection(URL, "sa", "scce");
} catch (Exception e) {
e.printStackTrace();
}
return con;
}
/**************************************************** 执行SQL语句 *********************************************************/
// 运行有结果集,无参数的sql语句
public static Result runSelectSql(String sql) {
Connection con = null;
PreparedStatement ps = null;
ResultSet res = null;
Result result = null;
try {
con = getConnection();
ps = con.prepareStatement(sql);
res = ps.executeQuery();
result = ResultSupport.toResult(res);
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
res.close();
ps.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
return result;
}
// 运行有结果集,有参数的sql语句
public static Result runSelectSql(String sql, Object[] params) {
Connection con = null;
PreparedStatement ps = null;
ResultSet res = null;
Result result = null;
try {
con = getConnection();
ps = con.prepareStatement(sql);
for (int i = 0; i ps.setObject(i + 1, params[i]);
}
res = ps.executeQuery();
result = ResultSupport.toResult(res);
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
res.close();
ps.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
return result;
}
// 运行无结果集,无参数的sql语句
public static boolean runUpdateSql(String sql) {
Connection con = null;
PreparedStatement ps = null;
try {
con = getConnection();
ps = con.prepareStatement(sql);
ps.executeUpdate();
return true;
} catch (Exception e) {
e.printStackTrace();
return false;
} finally {
try {
ps.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
// 运行无结果集,有参数的sql语句
public static boolean runUpdateSql(String sql, Object[] params) {
Connection con = null;
PreparedStatement ps = null;
try {
con = getConnection();
ps = con.prepareStatement(sql);
for (int i = 0; i ps.setObject(i + 1, params[i]);
}
ps.executeUpdate();
return true;
} catch (Exception e) {
e.printStackTrace();
return false;
} finally {
try {
ps.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
/**************************************************** 执行存储过程语句 *********************************************************/
// 无结果集,无参数的存储过程
public static boolean runUpdateByProc(String procName) {
Connection con = null;
CallableStatement cs = null;
try {
con = getConnection();
String proc = String.format("{call %s()}", procName);
cs = con.prepareCall(proc);
return cs.executeUpdate() > 0;
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
cs.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
return false;
}
// 无结果集,有参数的存储过程
public static boolean runProcUpdate(String procName, Object[] params) {
Connection con = null;
CallableStatement cs = null;
try {
con = getConnection();
String proc = "{call " + procName + "(";
for (int i = 0; i proc += "?,";
}
proc = proc.substring(0, proc.length() - 1) + ")}";
cs = con.prepareCall(proc);
for (int i = 0; i // 说明是输入参数
if (params[i] != null) {
cs.setObject(i + 1, params[i]);
}
// 否则输出参数,就要注册
else {
// 第一个为位置,第二个为类型
cs.registerOutParameter(i + 1, java.sql.Types.VARCHAR);
}
}
cs.executeUpdate();// 只是执行了存储过程,但是还没有把执行赋给输出参数
for (int i = 0; i if (params[i] == null) { // 说明是输出参数
params[i] = cs.getObject(i + 1);
}
}
return true;
} catch (Exception e) {
e.printStackTrace();
return false;
} finally {
try {
cs.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
// 有结果集,无参数的存储过程
public static Result runSelectByProc(String procName) {
Connection con = null;
ResultSet res = null;
Result result = null;
CallableStatement cs = null;
try {
con = getConnection();
String proc = String.format("{call %s}", procName);
cs = con.prepareCall(proc);
res = cs.executeQuery();
result = ResultSupport.toResult(res);
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
res.close();
cs.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
return result;
}
// 有结果集,有参数的存储过程
public static Result runSelectByProc(String procName, Object[] params) {
Connection con = null;
PreparedStatement ps = null;
ResultSet res = null;
Result result = null;
CallableStatement cs = null;
try {
con = getConnection();
String proc = "{call " + procName + "(";
for (int i = 0; i proc += "?,";
}
proc = proc.substring(0, proc.length() - 1) + ")}";
cs = con.prepareCall(proc);
for (int i = 0; i if (params[i] != null)
{
cs.setObject(i + 1, params[i]);
} else
{
cs.registerOutParameter(i + 1, java.sql.Types.VARCHAR);
}
}
res = cs.executeQuery();
result = ResultSupport.toResult(res);
for (int i = 0; i if (params[i] == null)
{
params[i] = cs.getObject(i + 1);
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
cs.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
return result;
}
}

ACID attributes include atomicity, consistency, isolation and durability, and are the cornerstone of database design. 1. Atomicity ensures that the transaction is either completely successful or completely failed. 2. Consistency ensures that the database remains consistent before and after a transaction. 3. Isolation ensures that transactions do not interfere with each other. 4. Persistence ensures that data is permanently saved after transaction submission.

MySQL is not only a database management system (DBMS) but also closely related to programming languages. 1) As a DBMS, MySQL is used to store, organize and retrieve data, and optimizing indexes can improve query performance. 2) Combining SQL with programming languages, embedded in Python, using ORM tools such as SQLAlchemy can simplify operations. 3) Performance optimization includes indexing, querying, caching, library and table division and transaction management.

MySQL uses SQL commands to manage data. 1. Basic commands include SELECT, INSERT, UPDATE and DELETE. 2. Advanced usage involves JOIN, subquery and aggregate functions. 3. Common errors include syntax, logic and performance issues. 4. Optimization tips include using indexes, avoiding SELECT* and using LIMIT.

MySQL is an efficient relational database management system suitable for storing and managing data. Its advantages include high-performance queries, flexible transaction processing and rich data types. In practical applications, MySQL is often used in e-commerce platforms, social networks and content management systems, but attention should be paid to performance optimization, data security and scalability.

The relationship between SQL and MySQL is the relationship between standard languages and specific implementations. 1.SQL is a standard language used to manage and operate relational databases, allowing data addition, deletion, modification and query. 2.MySQL is a specific database management system that uses SQL as its operating language and provides efficient data storage and management.

InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB


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