mysql数据库Insert语句后面加ON DUPLICATE KEY UPDATE，保证唯一性

如果在INSERT语句末尾指定了ON DUPLICATE KEY UPDATE，并且插入行后会导致在一个UNIQUE索引或PRIMARY KEY中出现重复值，则在出现重复值的行执行UPDATE；如果不会导致唯一值列重复的问题，则插入新行。

 

例如：

 

 

建表语句：

CREATE TABLE `consume_locus` (
`rds` varchar(255) NOT NULL,
`topic` varchar(255) default NULL,
`createTime` datetime default NULL,
`dtsTime` datetime default NULL,
PRIMARY KEY  (`rds`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

sql语句：

insert into t_tableName(topic,createTime,dtsTime,rds ) values( null,'2017-02-08 14:02:50','','' )  on duplicate key update topic = values(topic),createTime = values(createTime),dtsTime = values(dtsTime),rds = values(rds) ;

 

这可以保证主键只有一条记录。

附上一段java代码，算是工具类。根据传入BEAN生成SQL语句。

package dbTest;

import java.util.Map;

public class DbBean {
//列名和列值
private Map<String, String> fieldMap;
//表名
private String tablename;
public Map<String, String> getFieldMap() {
return fieldMap;
}
public void setFieldMap(Map<String, String> fieldMap) {
this.fieldMap = fieldMap;
}
public String getTablename() {
return tablename;
}
public void setTablename(String tablename) {
this.tablename = tablename;
}

}

 

public class testDB {

public static void main(String args[]) throws InterruptedException{
String createTimeStr=DateUtil.dateToStr(new Date(), DateUtil.YYYYMMDDHHMMSS2);
Map<String, String> fieldMap=new HashMap<String, String>();
fieldMap.put("rds", ClusterClientCore.rdsCode);
fieldMap.put("topic", ClusterClientCore.topic);
fieldMap.put("createTime", createTimeStr);
fieldMap.put("dtsTime", ClusterClientCore.dtsTimestamp);
DbBean bean =new DbBean();
bean.setFieldMap(fieldMap);
bean.setTablename("t_tableName");
String sql=getInsertSqlStr(bean);
System.out.println(sql);
}

/**
* 把bean转换为sql语句
* @param bean
* @return
*/
public static String getInsertSqlStr(DbBean bean){
StringBuffer columName=new StringBuffer();
StringBuffer columValue=new StringBuffer();
//幂等操作
StringBuffer duplicateSb=new StringBuffer();
Map<String, String> fieldMap=bean.getFieldMap();
Iterator it=fieldMap.entrySet().iterator();
while(it.hasNext()){
Map.Entry<String, Object> entry=(Map.Entry<String, Object>)it.next();
String key=entry.getKey();
duplicateSb.append(key).append(" = values(").append(key).append("),");
columName.append(key).append(",");
if(entry.getValue()!=null){
String value=(String)entry.getValue();
columValue.append("'").append(value).append("'").append(",");
}else{
columValue.append(entry.getValue()).append(",");
}
}
String columNameStr=columName.deleteCharAt(columName.length()-1).toString();
String columValueStr=columValue.deleteCharAt(columValue.length()-1).toString();
String sqlStr="insert into "+ bean.getTablename()+"("+columNameStr+" ) values( "+columValueStr+" ) ";
String duplicateStr=" on duplicate key update "+duplicateSb.deleteCharAt(duplicateSb.length()-1).toString()+" ;";
return sqlStr+duplicateStr;
}
}