我有几张桌子。我也有查询。我的问题是使用Java动态生成SQL查询。
我在单独的表格中有以下字段：
Collumn name status
po_number, Y
unit_cost, Y
placed_date , Y
date_closed, Y
scheduled_arrival_date Y
date_closed Y
order_quantity Y
roll_number N
product_sku N
product_category_name N
rec_vendor_quantity Y
vendor_name Y
et_conversion_unit_quantity Y
我必须在状态为Y时生成查询，这里的问题是上述列的一段时间
以下查询是上述的输出：
这里我已经包含了所有列但我必须删除状态为N的列，请帮助我使用java来解决查询。
select
pi.po_number,poi.unit_cost,pi.placed_date CreateDate,
case when isnull(pi.date_closed) then pi.scheduled_arrival_date
else pi.date_closed end as ReceviedDate,
poi.order_quantity,poi.roll_number,p.product_sku product_name,
pc.product_category_name,poi.rec_vendor_quantity,pv.vendor_name,p.et_conversion_unit_quantity,pi.note
from
purchase_order as pi,
purchase_order_inventory as poi,
product_vendors as pv,
products AS p,
product_categories AS pc
where
pi.purchase_order_id=poi.purchase_order_id and
pc.product_category_id=p.product_category_id and
poi.product_id = p.product_id and
poi.product_category_id=pc.product_category_id and
pi.vendor_id=pv.product_vendor_id and
( ( pi.date_closed >= '2012-01-01' and pi.date_closed <='2012-09-05 23:59:59' )
or ( pi.scheduled_arrival_date >= '2012-01-01' and pi.scheduled_arrival_date <='2012-09-05 23:59:59') ) and
pi.po_type=0
and pi.status_id = 0 and poi.transaction_type = 0
order by pi.po_number
更新：
QUERY：STEP 1:
SELECT rcm.id,rcm.tablename,rcm.columnname,rcm.size,rcm.displayorder,rcm.isactive FROM report_customise_master rcm where rcm.tablename !='employee' and rcm.isactive='Y' order by rcm.displayorder;
第2步： 用于构造查询的Java方法：
public Map getComplexReportQuery() {
String query = "SELECT rcm.id,rcm.tablename,rcm.columnname,rcm.size,rcm.displayorder,rcm.isactive FROM report_customise_master rcm where rcm.tablename !='employee' and rcm.isactive='Y' order by rcm.displayorder;";
String tableName = "", from = "", select = "";
StringBuffer sb = new StringBuffer();
Map<String, List<String>> resultsMap = new LinkedHashMap<String, List<String>>();
Map<String, String> displayOrderMap = new LinkedHashMap<String, String>();
Map queryMap = new LinkedHashMap();
if (!query.isEmpty() || query.length() > 0) {
sb.append(query);
}
Connection connection = getConnection();
if (connection != null) {
try {
PreparedStatement reportQueryPS = connection.prepareStatement(sb.toString());
ResultSet reportQuery_rst = reportQueryPS.executeQuery();
List<String> tables = new ArrayList<String>();;
if (reportQuery_rst != null) {
StringBuilder selectQuery = new StringBuilder(" SELECT ");
StringBuilder fromQuery = new StringBuilder(" FROM ");
while (reportQuery_rst.next()) {
tableName = reportQuery_rst.getString("tablename");
List<String> columns = resultsMap.get(tableName);
if (columns == null) {
columns = new ArrayList<String>();
resultsMap.put(tableName, columns);
}
columns = resultsMap.get(tableName);
String columnName = reportQuery_rst.getString("columnname");
columns.add(columnName);
}
tableName = "";
for (Entry<String, List<String>> resultEntry : resultsMap.entrySet()) {
tableName = resultEntry.getKey();
List<String> columns = resultEntry.getValue();
int i = 0;
for (String column : columns) {
selectQuery.append(tableName + "." + column);
if (i != columns.size()) {
selectQuery.append(",");
} else {
selectQuery.append("");
}
i++;
}
if (!tables.contains(tableName)) {
tables.add(tableName);
}
}
//to remove comma at the end of line
select = selectQuery.toString().replaceAll(",$", "");
tableName = "";
int i = 0;
for (String table : tables) {
fromQuery.append(table);
fromQuery.append(" ");
fromQuery.append(table);
if (i != tables.size()) {
fromQuery.append(",");
} else {
fromQuery.append("");
}
i++;
}
from = fromQuery.toString().replaceAll(",$", "");
queryMap.put("query", select + from);
}
//from = from+"ORDER BY "+orderbyColumn+" "+sort+" ";
} catch (Exception ex) {
ex.printStackTrace();
} finally {
try {
closeConnection(connection, null, null);
} catch (Exception ex) {
ex.printStackTrace();
}
}
} else {
System.out.println("Connection not Established. Please Contact Vendor");
}
return queryMap;// return the map/ list which contains query and sory and display order
}
第3步：结果查询
{query= SELECT purchase_order.po_number,purchase_order.placed_date,purchase_order.date_closed,purchase_order.scheduled_arrival_date,purchase_order_inventory.unit_cost,purchase_order_inventory.order_quantity,purchase_order_inventory.roll_number,purchase_order_inventory.rec_vendor_quantity,products.product_sku,products.et_conversion_unit_quantity,product_categories.product_category_name ,product_vendors.vendor_name FROM purchase_order purchase_order,purchase_order_inventory purchase_order_inventory,products products,product_categories product_categories,product_vendors product_vendors}
但这不是我想要的，请帮我构建我给出的查询。
答案 0 :(得分：2)
两次查询
您需要进行两次查询：
就是这样，因为SQL查询必须告诉在查询任何数据之前将包含哪些列。事实上，它将用于构建内部数据库查询计划，它是数据库电机用于检索和组织您询问的数据的方式。
查询所有列
只查询那些字段是否必要？你不能查询所有内容并使用相关数据吗？
<强>加入
查看更新后的问题我想你需要动态添加条件以正确连接表。我应该做的是有一个参考，告诉我当桌子存在时要添加什么样的记录。
至少有两个选择：
根据您的示例，我认为第二个选项更适合（并且易于实现）。
所以我应该有一些静态Map<String, JoinInfo>，其中JoinInfo至少有：
JoinInfo
+ conditionToAdd // by example "A.col1 = B.col2"
+ dependsOnTable // by example "A" to indicate that A must be present when B is present
所以你可以使用：
无论如何......我觉得你遇到了很多麻烦。为什么这么有活力？
答案 1 :(得分：2)
你必须一步一步地接近这件事。
首先，您必须创建一个返回所有status='Y'
然后，您将把COLUMN_NAME放入字符串列表中。
List<String> list = new List<String>();
while(rs.next()){
list.add(rs.getString(columnNumber));
}
然后你必须循环List并动态生成你的第二个sql语句
String sqlSelect = "SELECT ";
String sqlFrom = " FROM SOME_OTHER_TABLE "
String sqlWhere = " WHERE SOME_CONDITION = 'SOME_VALUE' "
for(String x : list){
sqlFrom += x +" , "+;
}
//here make sure that you remove the last comma from sqlFrom because you will get an SQLException
String finalSql = sqlSelect + sqlFrom + sqlWhere ;