Question

我创建了一个TabLayout，我想通过所选标签显示我的数据库条目。以下是包含查询的代码段：

public Cursor filteredItems(int tabPosition) throws SQLException {
        Log.d(TAG, "filteredItems called, Parameter: "+tabPosition); 

        String filter = ""; 
        if(tabPosition == 0){
            filter = "[a-cA-C]%";
        }else if(tabPosition == 1){
            filter = "[d-fD-F]%";
        }else{
            Log.d(TAG, "default tab"); 
            filter = "[a-zA-Z]%";
        }

        Cursor cursor = null;
        try{
            open();
            String query ="SELECT _id, surname, prename, street, zipcode, telephone, email FROM "+Database.getMyDbTable()+" " +
                    "WHERE surname LIKE '"+filter+"';";
            Log.d(TAG,"Query "+query);
            cursor = database.rawQuery(query, null);
        }catch(Exception ex){
            Log.e(TAG, "Could not get list");
            CharSequence text = dataNotFound;
            Toast toast = Toast.makeText(context, text, duration);
            toast.show();
        }

        return cursor;
    }

不幸的是，过滤器不起作用 - 查询的结果总是为空（表不是空的 - 我已经检查过了）。

Answer 1

您需要为此目的使用通配符。阅读http://sqlite.awardspace.info/syntax/sqlitepg03.htm

尝试

SELECT _id, surname, prename, street, zipcode, telephone, email FROM table WHERE surname LIKE '<your letter(s)>%'

Answer 2

首先，LIKE运算符不采用正则表达式。不幸的是，在Android中不支持执行此操作的REGEXP运算符。

解决方案：使用LIKE和逻辑OR。

String query ="SELECT _id, surname, prename, street, zipcode, telephone, email FROM "+Database.getMyDbTable()+" WHERE surname LIKE 'a%' OR surname LIKE 'b%' OR surname LIKE 'c%';";

Answer 3

尝试类似：

"SELECT _id, surname, prename, street, zipcode, telephone, email FROM " + Database.getMyDbTable() + " WHERE substr(" + Database.getMyDbTable()  +",1) LIKE " + <yourletter>

使用substr，您只比较第一个字母。

Answer 4

LIKE无法与字符集匹配。

由于您只关心第一个字母，因此您可以使用BETWEEN代替：

SELECT ... FROM MyTable WHERE surname BETWEEN 'A' AND 'Czzzz'

要处理大写和小写，请使用两个条件，或更改排序规则：

SELECT ... FROM MyTable WHERE surname BETWEEN 'A' AND 'Czzzz'
                           OR surname BETWEEN 'a' AND 'czzzz'

SELECT ... FROM MyTable WHERE surname COLLATION UNICODE BETWEEN 'A' AND 'Czzzz'

只有在使用相同的排序规则声明列或索引时，后者才能使用索引。

通过条目的第一个字母查询sqlite数据库

4 个答案: