Sqlite query & rawQuery

概述场景： 今天在写代码的时候被责令重构，凡是使用rawQuery的地方一律改为使用query，原因无他，可防SQL注入，并且由于query的参数一段段都是分开的，所以推荐使用Query。 比如我要查询我数据库里某张表最后一条状态为onGoing状态的数据代码如下： rawQuery public Visit getLastData() { //todo Curso

场景：

今天在写代码的时候被责令重构，凡是使用rawquery的地方一律改为使用query，原因无他，可防sql注入，并且由于query的参数一段段都是分开的，所以推荐使用query。

比如我要查询我数据库里某张表最后一条状态为onGoing状态的数据代码如下：

rawquery

  public Visit getLastData() {        //todo        Cursor cursor = database.rawquery("SELECT * FROM " + table + " where status = "+Visit.STATUS_ONGOING+" ORDER BY androID_ID DESC liMIT 1",null);        cursor.movetoFirst();        return cursorToEntity(cursor);    }

自己拼接SQL语句，一不小心就会写错. query

     /**     * get last ongoing visit in database.     * @return     */    public Visit getLastOngoingVisit() {        String[] columns = null;        String selection = VisitDB.Visit.ColUMN_STATUS + "=?";        String[] selectionArgs = {String.valueOf(Visit.STATUS_ONGOING)};        String orderby = VisitDB.Visit.ColUMN_ANDROID_ID+" DESC";        String limit = "1";        Cursor cursor = database.query(table,columns,selection,selectionArgs,null,orderby,limit);        cursor.movetoFirst();        return cursorToEntity(cursor);    }

这样似乎很清晰吧

关于query各个参数说明

 /**     * query the given table,returning a {@link Cursor} over the result set.     *     * @param table The table name to compile the query against.     * @param columns A List of which columns to return. Passing null will     *            return all columns,which is discouraged to prevent reading     *            data from storage that isn't going to be used.     * @param selection A filter declaring which rows to return,formatted as an     *            sql WHERE clause (excluding the WHERE itself). Passing null     *            will return all rows for the given table.     * @param selectionArgs You may include ?s in selection,which will be     *         replaced by the values from selectionArgs,in order that they     *         appear in the selection. The values will be bound as Strings.     * @param groupBy A filter declaring how to group rows,formatted as an sql     *            GROUP BY clause (excluding the GROUP BY itself). Passing null     *            will cause the rows to not be grouped.     * @param having A filter declare which row groups to include in the cursor,*            if row grouPing is being used,formatted as an sql HAVING     *            clause (excluding the HAVING itself). Passing null will cause     *            all row groups to be included,and is required when row     *            grouPing is not being used.     * @param orderBy How to order the rows,formatted as an sql ORDER BY clause     *            (excluding the ORDER BY itself). Passing null will use the     *            default sort order,which may be unordered.     * @param limit limits the number of rows returned by the query,*            formatted as liMIT clause. Passing null denotes no liMIT clause.     * @return A {@link Cursor} object,which is positioned before the first entry. Note that     * {@link Cursor}s are not synchronized,see the documentation for more details.     * @see Cursor     */

对于sqlite的limit跟MysqL还是有区别的，有个offset关键字，可忽略多少条记录进行查询多少条数据，具体的不赘述，自己实验使用吧。 总结

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