FIELD_id是表中的一个字段名,where = FIELD_id +"= ?" 表示查询的条件。 ?代表的是你要查询的记录中对应的FIELD_id字段的值,如果用sql来表示应该大概是这样: select * from table where FIELD_id=? 我举的这个例子代表查询table中FIELD_id的值为?的记录,?可以通过程序赋值成具体的值。
还是不大明白啊:代码里面是这个样子的额: private final static String DATABASE_NAME = "todo_db"; private final static int DATABASE_VERSION = 1; private final static String TABLE_NAME = "todo_table"; public final static String FIELD_id = "_id"; public final static String FIELD_TEXT = "todo_text";public void delete(int id) { SQLiteDatabase db = this.getWritableDatabase(); String where = FIELD_id + " = ?"; String[] whereValue = { Integer.toString(id) }; db.delete(TABLE_NAME, where, whereValue); }
还是不大明白啊:代码里面是这个样子的额: private final static String DATABASE_NAME = "todo_db"; private final static int DATABASE_VERSION = 1; private final static String TABLE_NAME = "todo_table"; public final static String FIELD_id = "_id"; public final static String FIELD_TEXT = "todo_text";public void delete(int id) { SQLiteDatabase db = this.getWritableDatabase(); String where = FIELD_id + " = ?"; String[] whereValue = { Integer.toString(id) }; db.delete(TABLE_NAME, where, whereValue); } 我一般不用这种写法,都是直接写SQL这个的意思是 delete * from table_name where field_id = wherevalue
还是不大明白啊:代码里面是这个样子的额: private final static String DATABASE_NAME = "todo_db"; private final static int DATABASE_VERSION = 1; private final static String TABLE_NAME = "todo_table"; public final static String FIELD_id = "_id"; public final static String FIELD_TEXT = "todo_text";public void delete(int id) { SQLiteDatabase db = this.getWritableDatabase(); String where = FIELD_id + " = ?"; String[] whereValue = { Integer.toString(id) }; db.delete(TABLE_NAME, where, whereValue); }
android里面对于sql语句的操作封装到了方法里,可以调用这个方法,也可以直接执行sql语句,用熟了更加方便 调用delete(int id)方法,只要传入一个参数比如说2,就可以删除指定数据库里指定表里id为2的所有记录 效果同直接执行sql语句:delete * from todo_table where FIELD_id=2
?代表的是你要查询的记录中对应的FIELD_id字段的值,如果用sql来表示应该大概是这样:
select * from table where FIELD_id=?
我举的这个例子代表查询table中FIELD_id的值为?的记录,?可以通过程序赋值成具体的值。
还是不大明白啊:代码里面是这个样子的额: private final static String DATABASE_NAME = "todo_db";
private final static int DATABASE_VERSION = 1;
private final static String TABLE_NAME = "todo_table";
public final static String FIELD_id = "_id";
public final static String FIELD_TEXT = "todo_text";public void delete(int id)
{
SQLiteDatabase db = this.getWritableDatabase();
String where = FIELD_id + " = ?";
String[] whereValue =
{ Integer.toString(id) };
db.delete(TABLE_NAME, where, whereValue);
}
还是不大明白啊:代码里面是这个样子的额: private final static String DATABASE_NAME = "todo_db";
private final static int DATABASE_VERSION = 1;
private final static String TABLE_NAME = "todo_table";
public final static String FIELD_id = "_id";
public final static String FIELD_TEXT = "todo_text";public void delete(int id)
{
SQLiteDatabase db = this.getWritableDatabase();
String where = FIELD_id + " = ?";
String[] whereValue =
{ Integer.toString(id) };
db.delete(TABLE_NAME, where, whereValue);
}
我一般不用这种写法,都是直接写SQL这个的意思是 delete * from table_name where field_id = wherevalue
private final static int DATABASE_VERSION = 1;
private final static String TABLE_NAME = "todo_table";
public final static String FIELD_id = "_id";
public final static String FIELD_TEXT = "todo_text";public void delete(int id)
{
SQLiteDatabase db = this.getWritableDatabase();
String where = FIELD_id + " = ?";
String[] whereValue =
{ Integer.toString(id) };
db.delete(TABLE_NAME, where, whereValue);
}
android里面对于sql语句的操作封装到了方法里,可以调用这个方法,也可以直接执行sql语句,用熟了更加方便
调用delete(int id)方法,只要传入一个参数比如说2,就可以删除指定数据库里指定表里id为2的所有记录
效果同直接执行sql语句:delete * from todo_table where FIELD_id=2