SQLiteDatabase选择具有动态数量的条件
我是数据库新手,所以这可能很简单。 我有以下数据库结构: 桌上产品 表过滤器(可能包含类似的内容)SQLiteDatabase选择具有动态数量的条件,sql,sqlite,select,join,Sql,Sqlite,Select,Join,我是数据库新手,所以这可能很简单。 我有以下数据库结构: 桌上产品 表过滤器(可能包含类似的内容) 蓝色 黑色 红色 小号 品牌X 表关系(只有产品id和筛选器id) 假设我想获得所有黑色或红色的小产品,我编写了以下查询: SELECT products.name FROM products JOIN pfrelation ON ((pfrelation.filter_id=18) AND (pfrelation.filter_id=11 OR pfrelation.filter_
- 蓝色
- 黑色
- 红色
- 小号
- 品牌X
SELECT products.name FROM products
JOIN pfrelation ON
((pfrelation.filter_id=18) AND (pfrelation.filter_id=11 OR pfrelation.filter_id=13) AND products.id=pfrelation.product_id)
在上面的示例中,11和13表示黑色和红色,而18表示小的id。因为您可能怀疑上述查询没有结果(id不能同时为18和11/13)。如何编写select以动态添加任何过滤器组合?如何重写上面示例中的查询
谢谢您可以通过动态查询来实现这一点。 我对PostgreSql不太了解,但我了解SQL Server,所以我举了一个例子来说明这一点
我通过以下方式动态构建查询:
public ArrayList<Products> getFilteredOnlinePictures( Hashtable<String, List<String>> filters,..)
{
SQLiteDatabase db = getWritableDatabase();
// create query conditions
StringBuffer filtersQuery = new StringBuffer();
for (String key: Collections.list(filters.keys()))
{
List<String> filtersValues = filters.get(key);
if (filtersQuery.length() > 0)
filtersQuery.append(" INTERSECT ");
filtersQuery.append("SELECT " + TABLE_PFRELATIONS + "." + COLUMN_PRODUCT_ID
+ " FROM " + TABLE_PFRELATIONS + " WHERE " + TABLE_PFRELATIONS + "."
+ COLUMN_FILTER_ID + " IN (");
for (String value: filtersValues)
{
long filterID = getIDForFilter(db, key, value);
filtersQuery.append(filterID);
if (filtersValues.indexOf(value) == (filtersValues.size() - 1))
{
// this is the last value
filtersQuery.append(")");
}
else
{
// there are more values
filtersQuery.append(",");
}
}
}
if (filtersQuery.length() > 0)
{
filtersQuery.append(")");
filtersQuery.insert(0, " WHERE " + TABLE_PRODUCTS + ".id" + " IN (");
}
String sql = "SELECT " + TABLE_PRODUCTS + "." + COLUMN_NAME + " FROM " + TABLE_PRODUCTS + filtersQuery.toString();
Cursor c = db.rawQuery(sql, null); ...
通过这种方式,我可以使用任意数量的值进行任何筛选。谢谢,同时我自己也做了类似的事情(我写了下面的内容以供进一步参考),但我会接受您的回答:)
public ArrayList<Products> getFilteredOnlinePictures( Hashtable<String, List<String>> filters,..)
{
SQLiteDatabase db = getWritableDatabase();
// create query conditions
StringBuffer filtersQuery = new StringBuffer();
for (String key: Collections.list(filters.keys()))
{
List<String> filtersValues = filters.get(key);
if (filtersQuery.length() > 0)
filtersQuery.append(" INTERSECT ");
filtersQuery.append("SELECT " + TABLE_PFRELATIONS + "." + COLUMN_PRODUCT_ID
+ " FROM " + TABLE_PFRELATIONS + " WHERE " + TABLE_PFRELATIONS + "."
+ COLUMN_FILTER_ID + " IN (");
for (String value: filtersValues)
{
long filterID = getIDForFilter(db, key, value);
filtersQuery.append(filterID);
if (filtersValues.indexOf(value) == (filtersValues.size() - 1))
{
// this is the last value
filtersQuery.append(")");
}
else
{
// there are more values
filtersQuery.append(",");
}
}
}
if (filtersQuery.length() > 0)
{
filtersQuery.append(")");
filtersQuery.insert(0, " WHERE " + TABLE_PRODUCTS + ".id" + " IN (");
}
String sql = "SELECT " + TABLE_PRODUCTS + "." + COLUMN_NAME + " FROM " + TABLE_PRODUCTS + filtersQuery.toString();
Cursor c = db.rawQuery(sql, null); ...
SELECT products.name FROM products
WHERE products.id IN (
SELECT pfrelation.product_id FROM pfrelation WHERE pfrelation.filter_id IN (18)
INTERSECT
SELECT pfrelation.product_id FROM pfrelation WHERE pfrelation.filter_id IN (11,13)
)