Java对数据库的调用一些常用方法总结

本篇博客知识点

1.executeQuery:方法

2.execute方法

3.executeUpdate方法

4，两种获得自动增长的主键方法~

5.学习用jdbc执行批处理

本篇博客调用的数据库为book 表结构如下

executeQuery:专门用于查询的方法。返回值为查询结果

/**
* executeQuery:专门用于查询的方法。返回值为查询结果
* @throws Exception
*/
@Test
public void demo1() throws Exception{
Connection con = ConnUtils.getConnection();
Statement st = con.createStatement();
String sql = "select * from book";
ResultSet rs= st.executeQuery(sql);
while(rs.next()){
int id = rs.getInt(1);
String name = rs.getString("name");
Double price = rs.getDouble("price");

String date = rs.getDate("birth")+" "+rs.getTime("birth");
System.out.println("编号:"+id+",书名:"+name+",价格:"+price+",时间"+date);
}
con.close();
}

细节：rs.getString(参数）,参数可以给序号，也可以给字段名字

execute：可以用于增、删、改、查。返回值为 boolean型 只有当执行查询时返回值为true

/**
* execute：可以用于增、删、改、查。返回值为 boolean型  只有当执行查询时返回值为true
* @throws Exception
*/
@Test
public void demo2() throws Exception{
Connection con = ConnUtils.getConnection();
Statement st = con.createStatement();
String sql_select = "select * from book where price>50";
String sql_insert = "insert into book(name,price,birth) values('资本论','105.3','1883-5-6 13:11:11');";
String sql_delete = "delete from book where id=1";
//update 表名  set 字段名1=值 ，字段名2=值 where 子句[in 子句] [between子句]
String sql_update = "update book set name='海燕',price=19.6 where id=1 ";
boolean boo = st.execute(sql_update);
if(boo){
ResultSet rs = st.getResultSet();
while(rs.next()){
int id = rs.getInt("id");
String name = rs.getString("name");
Double price = rs.getDouble("price");
String date = rs.getDate("birth")+""+rs.getTime("birth");
System.out.println("编号:"+id+",书名:"+name+",价格:"+price+",时间"+date);
}
}
con.close();
}

executeUpdate: 除了不能用于查询外，其他增、删、改都能执行，返回值为整形 n– 表示影响的行数

@Test
public void demo3() throws Exception{
Connection con = ConnUtils.getConnection();
Statement st = con.createStatement();
//      String sql_select = "select * from book where price>50";
String sql_insert = "insert into book(name,price,birth) values('生物进化论','105.3','1883-5-6 13:11:11');";
String sql_delete = "delete from book where id=1";
//update 表名  set 字段名1=值 ，字段名2=值 where 子句[in 子句] [between子句]
String sql_update = "update book set name='海燕',price=19.6 where id=1 ";
int n = st.executeUpdate(sql_insert);
System.out.println(n);
con.close();
}

通过statemnet获得自动增长的主键~ 插入的时候

/**
* 通过statemnet获得自动增长的主键~ 插入的时候
* st.executeUpdate(sql, Statement.RETURN_GENERATED_KEYS);
* st.getGeneratedKeys();
* @throws Exception
*/
@Test
public void getAuto() throws Exception{
Connection con  = ConnUtils.getConnection();
Statement st = con.createStatement();
String sql_insert = "insert into book(name,price,birth) values('达尔文','105.3','1883-5-6 13:11:11');";
String sql = "insert into book(name,price,birth) values('海子诗集',79.8,'1996-4-8 8:30:5')";
int n = st.executeUpdate(sql, Statement.RETURN_GENERATED_KEYS);
ResultSet rs = st.getGeneratedKeys();
if(rs.next()){
System.out.println("---------");
int id = rs.getInt(1);
System.out.println("插入之后获得自动增长ID:"+id);
}
con.close();

}

通过PreparedStatement获得自动增长的主键

/**
* 通过PreparedStatement获得自动增长的主键~ 插入的时候
*
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PreparedStatement pst = con.prepareStatement(sql, PreparedStatement.RETURN_GENERATED_KEYS);
* pst.getGeneratedKeys();
* @throws Exception
*/
@Test
public void getAuto2() throws Exception{
Connection con  = ConnUtils.getConnection();
String sql = "insert into book(name,price,birth) values(?,?,?)";
PreparedStatement pst = con.prepareStatement(sql, PreparedStatement.RETURN_GENERATED_KEYS);
String name = "唐诗宋词300首";
String price = "79.8";
String date = "1996-4-8 8:30:5";
pst.setString(1, name);
pst.setString(2, price);
pst.setString(3, date);
int n = pst.executeUpdate();
//***********
ResultSet rs = pst.getGeneratedKeys();
if(rs.next()){
System.out.println("---------");
int id = rs.getInt(1);
System.out.println("插入之后获得自动增长ID:"+id);
}
con.close();

}

jdbc执行批处理

方式一：

/**
* 学习用jdbc执行批处理 (把多条sql语句打包，一次性发给mysql数据库，让它执行。该方式能够减少客户端与MySQL服务器的通讯次数)
* 先打包addBatch
* 返回值为每一条sql语句影响的记录数的数组
* @throws Exception
*/
@Test
public void batchDemo1() throws Exception{
Connection con = ConnUtils.getConnection();
Statement st = con.createStatement();
String sql = "insert into book(name,price,birth) values('我的大学','18.5','2017-07-30 16:09:09')";
for(int i=0;i<5;i++){
// 打包到一起
st.addBatch(sql);
}
sql = "update book set price=price*1.5 where price>100";
st.addBatch(sql);
int n[] = st.executeBatch();
//n --- 1 1 1 1 1 7; 返回值为每一条sql语句影响的记录数
for(int i=0;i<n.length;i++){
System.out.println(n[i]);
}
con.close();
}

方式二

/**
* //           pst.addBatch(sql);---错误~  没有参数
* @throws Exception
*/
@Test
public void batchDemo2() throws Exception{
Connection con = ConnUtils.getConnection();
String sql = "insert into book(name,price,birth) values(?,?,?)";
PreparedStatement pst = con.prepareStatement(sql);
for(int i=0;i<5;i++){
pst.setString(1, "高等数学"+i);
pst.setDouble(2, 35+i);
pst.setString(3, "2017-07-30 16:09:09");

//          pst.addBatch(sql);---错误~  没有参数
pst.addBatch();
}
sql = "update book set price=price*1.5 where price>100";
pst.addBatch(sql);
int n[] = pst.executeBatch();
for(int i=0;i<n.length;i++){
System.out.println(n[i]);
}
con.close();
}