从 SQLite 数据库中删除所有已完成的项目

Posted 2023-04-19

【中文标题】从 SQLite 数据库中删除所有已完成的项目

【英文标题】：Deleting all done items from a SQLite databse

【发布时间】：2021-09-06 04:24:28

【问题描述】：

我需要从待办事项列表数据库中删除已完成的项目 (IS_ACTIVE = 1)，但我的代码只是清除了数据库。我的错误是什么？ Database example

    private val todoTable = "TODO_TABLE"
    private val isActive = "IS_ACTIVE"

    fun deleteDone()
        val db = this.writableDatabase
        val sqlSelectQuery = "SELECT * FROM $todoTable"
        val cursor = db.rawQuery(sqlSelectQuery, null)
        if(cursor.moveToFirst())
            do 
                val sqlDeleteQuery = "DELETE FROM $todoTable WHERE $isActive = $cursor.getInt(2) = 1"
                db.execSQL(sqlDeleteQuery)
            while(cursor.moveToNext())
        
        db.close()
    

【参考方案1】：

无需选择带有IS_ACTIVE = 1 的行，然后循环将它们一一删除。 使用delete()方法将其全部删除：

fun deleteDone()
    val db = this.writableDatabase
    db.delete(todoTable, isActive + " = 1", null)
    db.close()

这里delete()的第二个参数是WHERE子句，sql语句会被解释为：

DELETE FROM TODO_TABLE WHERE IS_ACTIVE = 1

或者更简单：

fun deleteDone()
    val db = this.writableDatabase
    db.delete(todoTable, isActive, null)
    db.close()

因为：

WHERE IS_ACTIVE

相当于：

WHERE IS_ACTIVE = 1

【参考方案2】：

试试下面的查询。

 if(cursor.getInt(2)==1)
 val sqlDeleteQuery = "DELETE FROM $todoTable WHERE $isActive = $cursor.getInt(2)" 
 db.execSQL(sqlDeleteQuery)