Question

我工作的公司使用第三方软件，我们没有接触过应用程序代码，因此我无法更改数据库对象。我试图在一个不是Sarg的视图中做一些工作，在视图中有一个colesce将null替换为0，并且在应用程序上调用视图，同一列上有一个过滤器。

SQL Server版本：2005

方案如下：

var arr = [{ "Id": 46489,
    "Message": "Hi",
    "MessageGroupId": 46488,
    "FlowId": 99
  },
  {
    "Id": 46492,
    "Message": "Hi User",
    "MessageGroupId": 46490,
    "FlowId": 100
  },
  {
    "Id": 46494,
    "Message": "Loan",
    "MessageGroupId": 46490,
    "FlowId": 101
  },
  {
    "Id": 46496,
    "Message": "Call",
    "MessageGroupId": 46490,
    "FlowId": 101
  }
]

Array.prototype.groupBy = function (props) {
   var arr = this;
   var partialResult = {};
   
   arr.forEach(el=>{
   
       var grpObj = {};
       
       props.forEach(prop=>{
             grpObj[prop] = el[prop]
       });
       
       var key = JSON.stringify(grpObj);
       
       if(!partialResult[key]) partialResult[key] = [];
       
       partialResult[key].push(el);
       
   });
   
   var finalResult = Object.keys(partialResult).map(key=>{
      var keyObj = JSON.parse(key);
      keyObj.values = partialResult[key];
      return keyObj;
   })
   
   return finalResult;
}


console.log(arr.groupBy(['MessageGroupId','FlowId']))

第一次测试 - Sarg问题

IF OBJECT_ID('test01' , 'U') IS NOT NULL
DROP TABLE test01;

CREATE TABLE test01 ( ID INT IDENTITY(1,1)  PRIMARY KEY
                     , Parent NVARCHAR(100)
                     );
                     GO

IF OBJECT_ID('test02' , 'U') IS NOT NULL
DROP TABLE test02;

CREATE TABLE test02 ( ID INT IDENTITY(1,1)  PRIMARY KEY
                    , ParentID INT 
                    , UserName NVARCHAR(100)
                    );
                    GO


ALTER TABLE test02 ADD CONSTRAINT FK_test02_ParentID FOREIGN KEY (ParentID) REFERENCES test02(ID);


INSERT INTO test01
          SELECT 'DGN010101'
UNION ALL SELECT 'DGN020202'
UNION ALL SELECT 'DGN030303'
UNION ALL SELECT 'DGN040404'
GO


INSERT INTO test02 (ParentID, UserName)
          SELECT 1, 'DGN010101'
UNION ALL SELECT 2, 'DGN020202'
UNION ALL SELECT NULL, 'DGN030303'
GO

第二次测试 - 没有sarg问题

--drop view vw_test 

CREATE VIEW vw_test 

AS

SELECT tmp1.ID as ParentID
     , tmp1.Parent
     , COALESCE(tmp2.ID, 0) as UserID
     , tmp2.UserName
FROM test01 tmp1
    LEFT JOIN test02 tmp2
        on tmp1.ID = tmp2.ID


------------------------
-- An index scan is performed 

SELECT ParentID
     , Parent
     , UserID
     , UserName
FROM vw_test
WHERE UserID = 1

要记住的事情：
- 我仍然需要将NULL替换为0.
- 我无法更改视图的调用方式。

我很感激你们的想法。

Answer 1

如果test02表的ID列（UserID）不允许NULL，请尝试以下版本：

CREATE VIEW vw_test2
AS
SELECT tmp1.ID as ParentID
     , tmp1.Parent
     , tmp2.ID as UserID
     , tmp2.UserName
FROM test01 tmp1
JOIN test02 tmp2
        on tmp1.ID = tmp2.ID
UNION ALL
SELECT tmp1.ID as ParentID
     , tmp1.Parent
     , 0 as UserID
     , tmp2.UserName
FROM test01 tmp1
LEFT JOIN test02 tmp2
        on tmp1.ID = tmp2.ID
WHERE tmp2.ID IS NULL;
GO

Coalesce vs Sargability

1 个答案: