Android under the database operation--adding and deleting changes

Android under the first way to delete and change the database

1. Create an object for the helper class, call the Getreadabledatabase method, and return a Sqlitedatebase object

2. Use Sqlitedatebase object Call Execsql () to do additions and deletions, call rawquery method to do the query.

Features: Additions and deletions without a return value, you cannot determine whether the SQL statement was executed successfully. SQL statements written manually, easy to write wrong



private Mysqliteopenhelper Mysqliteopenhelper;
Public Infodao (context context) {
//Create a helper class object
mysqliteopenhelper = new Mysqliteopenhelper (context);

        
    }

Public void Add (Infobean bean) {

//Execute SQL statement requires Sqlitedatabase object
//Call the Getreadabledatabase method to initialize the creation of the database
Sqlitedatabase db = Mysqliteopenhelper.getreadabledatabase ();
//sql:sql Statement, the value of the placeholder in the Bindargs:sql statement
Db.execsql ("INSERT into info (name,phone) values (?,?);", New Object[]{bean.name,bean.phone});
//Close database objects
db.close ();
    }

Public void del (String name) {


//Execute SQL statement requires Sqlitedatabase object
//Call the Getreadabledatabase method to initialize the creation of the database
Sqlitedatabase db = Mysqliteopenhelper.getreadabledatabase ();
//sql:sql Statement, the value of the placeholder in the Bindargs:sql statement
db.execsql ("delete from info where name=?;", New Object[]{name});
//Close database objects
db.close ();

    }
Public void Update (Infobean bean) {

//Execute SQL statement requires Sqlitedatabase object
//Call the Getreadabledatabase method to initialize the creation of the database
Sqlitedatabase db = Mysqliteopenhelper.getreadabledatabase ();
//sql:sql Statement, the value of the placeholder in the Bindargs:sql statement
db.execsql ("Update info set phone=?") where name=?; ", New Object[]{bean.phone,bean.name});
//Close database objects
db.close ();

    }
Public void Query (String name) {
        
//Execute SQL statement requires Sqlitedatabase object
//Call the Getreadabledatabase method to initialize the creation of the database
Sqlitedatabase db = Mysqliteopenhelper.getreadabledatabase ();
//sql:sql Statement, Selectionargs: The value of the query condition placeholder, returns a cursor object
cursor cursor = db.rawquery ("Select _id, name,phone from info where name =?", New String []{name});
//Parse data in cursor
if (cursor! = NULL && cursor.getcount () >0) {//Determine if data exists in the cursor
            
//Iterate through the result set to get the contents of each row
while (Cursor.movetonext ()) {//condition, whether the cursor can be positioned to the next row
//Get Data
int id = cursor.getint (0);
String name_str = cursor.getstring (1);
String phone = cursor.getstring (2);
System.out.println ("_id:" +id+ "; Name:" +name_str+ ";p Hone:" +phone);
            }
cursor.close ();//close result set
            
        }
//Close database objects
db.close ();

    }
    

another way to change and delete under Android
    
1. Create an object for the helper class, call the Getreadabledatabase method, and return a Sqlitedatebase object

2. Use Sqlitedatebase object call Insert,update,delete, query method to do additions and deletions to change.

features: Adding and deleting the return value, you can determine whether the SQL statement is successful, but the query is not flexible enough to do a long table query. So in the company of General people to increase the deletion like the second way, query in the first way.

private Mysqliteopenhelper Mysqliteopenhelper;
Public Infodao (context context) {
//Create a helper class object
mysqliteopenhelper = new Mysqliteopenhelper (context);
    }

Public Boolean Add (Infobean Bean) {

//Execute SQL statement requires Sqlitedatabase object
//Call the Getreadabledatabase method to initialize the creation of the database
Sqlitedatabase db = Mysqliteopenhelper.getreadabledatabase ();
        
        
contentvalues values = new Contentvalues ();//is a map-encapsulated object used to store values
values.put ("name", Bean.name);
values.put ("Phone", bean.phone);
        
//table: Table name, Nullcolumnhack: Can be empty, Mark adds a blank line, values: The value of the data row, the return value: Represents the ID of the new row added, 1 for add failed
Long result = Db.insert ("info", null, values);//The underlying is the SQL statement being assembled
    
//Close database objects
db.close ();
        
if (Result! =-1) {//-1 represents add failure
return true;
}else{
return false;
        }
    }

public int del (String name) {

//Execute SQL statement requires Sqlitedatabase object
//Call the Getreadabledatabase method to initialize the creation of the database
Sqlitedatabase db = Mysqliteopenhelper.getreadabledatabase ();
        
//table: Table name, Whereclause: Delete condition, Whereargs: The parameter of the placeholder for the condition; return value: How many rows were successfully deleted
int result = Db.delete ("info", "name =?", new String[]{name});
//Close database objects
db.close ();
        
return result;

    }
public int Update (Infobean bean) {

//Execute SQL statement requires Sqlitedatabase object
//Call the Getreadabledatabase method to initialize the creation of the database
Sqlitedatabase db = Mysqliteopenhelper.getreadabledatabase ();
contentvalues values = new Contentvalues ();//is a map-encapsulated object used to store values
values.put ("Phone", bean.phone);
//table: Table name, Values: Updated value, Whereclause: Updated condition, Whereargs: Update the value of the placeholder for the condition, return value: How many rows were successfully modified
int result = db.update ("info", values, "name =?", new String[]{bean.name});
//Close database objects
db.close ();
return result;

    }
Public void Query (String name) {
    
//Execute SQL statement requires Sqlitedatabase object
//Call the Getreadabledatabase method to initialize the creation of the database
Sqlitedatabase db = Mysqliteopenhelper.getreadabledatabase ();
        
//table: Table name, columns: The column name of the query, if NULL represents the query for all columns, selection: Query condition, Selectionargs: The parameter value of the conditional placeholder,
//groupby: Grouped by what field, having: grouping conditions, ORDER by: What field to sort
cursor cursor = db.query ("info", new string[]{"_id", "name", "Phone"}, "name =?", new String[]{name}, NULL, NUL L, "_id desc");
//Parse data in cursor
if (cursor! = NULL && cursor.getcount () >0) {//Determine if data exists in the cursor
            
//Iterate through the result set to get the contents of each row
while (Cursor.movetonext ()) {//condition, whether the cursor can be positioned to the next row
//Get Data
int id = cursor.getint (0);
String name_str = cursor.getstring (1);
String phone = cursor.getstring (2);
System.out.println ("_id:" +id+ "; Name:" +name_str+ ";p Hone:" +phone);
                
                
            }
cursor.close ();//close result set
            
        }
//Close database objects
db.close ();

    }

Android under the database operation--adding and deleting changes