Question

我尝试使用SELECT DISTINCT sql命令从数据库coulmn获取所有唯一值。但是当我的活动加载时我得到异常，我在logcat中有这个错误代码：

05-05 09:08:32.637: E/AndroidRuntime(1314): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.workoutlog/com.example.workoutlog.AddWorkOutPage}: android.database.sqlite.SQLiteException: near "SELECT": syntax error (code 1): , while compiling: SELECT * FROM exerciseTable WHERE SELECT DISTINCTexercise_typefromexerciseTable

我认为我没有正确编写命令，这是我的代码：

public String[] getAllExercies() {
        String selecet = "SELECT DISTINCT" + COLUMN_EXERCISE + "from" + TABLE_NAME;
        Cursor c = ourDatabase.query(TABLE_NAME, null, selecet, null, null, null, null);
        int dayExercise = c.getColumnIndex(COLUMN_EXERCISE);

        String[] list = new String[c.getCount()-1];
        int j = 0;
        for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()){
            list[j] = c.getString(dayExercise);
            j++;
        }

        return list;
    }

Answer 1

我认为您应首先查看这些答案here和here，以便查看.query（）函数的工作情况。请注意，使用ourDatabase.query()函数时，参数如下：

String Table Name: The name of the table to run the query against
String [ ] columns: The projection of the query, i.e., the columns to retrieve
String WHERE clause: where clause, if none then pass null
String [ ] selection args: The parameters of the WHERE clause
String Group by: A string specifying group by clause
String Having: A string specifying HAVING clause
String Order By by: A string Order By by clause

所以你的第三个变量应该是 WHERE 子句，类似于：

String[] args = { "first string" };
Cursor c = ourDatabase.query("TABLE_NAME", null, "exercise_type=?", args, null, null, null);

由于您不需要WHERE子句，因此您可能希望使用rawQuery（）方法。

String selecet = "SELECT DISTINCT " + COLUMN_EXERCISE + " FROM " + TABLE_NAME;
ourDatabase.rawQuery(selecet, null);

<强>更新尝试here的答案。做这样的事情：

Cursor c = ourDatabase.query(true, "exerciseTable", new String[] {"exercise_type"}, null, null, "exercise_type", null, null, null);
int dayExercise = c.getColumnIndex(COLUMN_EXERCISE);
//... continue with your further code

希望这有助于其他请评论。

Answer 2

<强>问题：你没有在单词之间保持space。

<强>阐释：

假设，String COLUMN_EXERCISE = "exercise";

和String TABLE_NAME = "tbl_workout";

然后 String selecet = "SELECT DISTINCT" + COLUMN_EXERCISE + "from" + TABLE_NAME;

只是意味着SELECT DISTINCTexercisefromtbl_workout

<强>解决方案：

String selecet = "SELECT DISTINCT " + COLUMN_EXERCISE + " from " + TABLE_NAME;

修改

请使用以下语法来激活rawQuery

Cursor c = ourDatabase.rawQuery(selecet,null);

我希望它会有所帮助！

Answer 3

您错过了查询中的所有空格，您应该替换为：

String selecet = "SELECT DISTINCT " + COLUMN_EXERCISE + " FROM " + TABLE_NAME;

从SQLite列获取字符串数组中的所有唯一值

3 个答案: