Как сравнить данные из нескольких баз данных

Question

Я пытаюсь сравнить некоторые данные из разных нескольких баз данных, поскольку я иллюстрирую свой текущий случай, у меня есть базы данных, база данных 1 является основной, и время от времени база данных 2 и база данных 3 обновляются из базы данных 1.У меня есть некоторые трудности, чтобы получить конечный результат, который возвращает данные из базы данных 1, а в двух столбцах столбца отображается доступность в базе данных 2 как Да или Нет, и то же самое со вторым дополнительным столбцом, который будет указывать на доступность данных в базе данных 3 с Даили нет

SELECT * 
FROM (
Select  ID      as  db1_ID,
    First_name  as  db1_First_name,
    Last_name   as  db1_Last_name,
    Email       as  db1_Email,
    Password    as  db1_Password,
    Request_Id  as  db1_Request_Id,
    User_Id     as  db1_User_Id,
    Request_name    as  db1_Request_name
from User 
inner join User_request 
on User_request.User_Id = user.ID
)   AS DB1_VIEW

LEFT OUTER JOIN 

(
Select  ID      as  db2_ID,
    First_name  as  db2_First_name,
    Last_name   as  db2_Last_name,
    Email       as  db2_Email,
    Password    as  db2_Password,
    Request_Id  as  db2_Request_Id,
    User_Id     as  db2_User_Id,
    Request_name    as  db2_Request_name
from User 
inner join User_request 
on User_request.User_Id = user.ID
)   AS DB2_VIEW

ON  db2_ID  = db1_ID 

LEFT OUTER JOIN 

(
Select  ID      as  db3_ID,
    First_name  as  db3_First_name,
    Last_name   as  db3_Last_name,
    Email       as  db3_Email,
    Password    as  db3_Password,
    Request_Id  as  db3_Request_Id,
    User_Id     as  db3_User_Id,
    Request_name    as  db3_Request_name
from User 
inner join User_request 
on User_request.User_Id = user.ID
)   AS DB3_VIEW

ON  db3_ID   = db1_ID

           ID   First_name  Last_name   Email   Password    Request_Id  User_Id Request_name
            1   Oliver  Jake    OJake@domain.com    123         1            1   Request1
            2   Mathew  Harry   MHarry@domain.com   123         1            2   Request1
            3   Jacob   Reece   JReece@domain.com   123         1            3 
Request1
            4   Charlie Damian  CDamian@domain.com  123         1            4   Request1

Answer 1

Для этого могут не потребоваться CTE или подзапросы.Несколько соединений могут сделать это.

SELECT
Usr1.ID AS db1_User_Id,
Usr1.First_name AS db1_First_name,
Usr1.Last_name AS db1_Last_name,
Usr1.Email AS db1_Email,
Usr1.Password AS db1_Password,
MAX(UsrReq1.Request_Id) AS db1_Request_Id,
MAX(UsrReq1.Request_name) AS db1_Request_name,
CASE WHEN COUNT(UsrReq2.User_Id) > 0 THEN 'Y' ELSE 'N' END AS Available_Db2,
CASE WHEN COUNT(UsrReq3.User_Id) > 0 THEN 'Y' ELSE 'N' END AS Available_Db3
FROM [Database1].[User] AS Usr1
LEFT JOIN [Database1].[User_request] AS UsrReq1 ON UsrReq1.User_Id = Usr1.ID
LEFT JOIN [Database2].[User] AS Usr2 ON Usr2.ID = Usr1.ID
LEFT JOIN [Database2].[User_request] AS UsrReq2 ON UsrReq2.User_Id = Usr2.ID
LEFT JOIN [Database3].[User] AS Usr3 ON Usr3.ID = Usr1.ID
LEFT JOIN [Database3].[User_request] AS UsrReq3 ON UsrReq3.User_Id = Usr3.ID
GROUP BY
Usr1.ID,
Usr1.First_name,
Usr1.Last_name,
Usr1.Email,
Usr1.Password;

Answer 2

Вы можете использовать приведенный ниже запрос перед выполнением, вы должны использовать replace [SourceDB] для вашей исходной базы данных и [TargertDB] для вашей целевой базы данных.Вставьте имя таблицы в #mdtables для включения в сравнение.

USE [SourceDB] 

IF Object_id('tempdb..#mdTables') IS NOT NULL 
  DROP TABLE #mdtables; 

CREATE TABLE #mdtables 
  ( 
     id         INT IDENTITY(1, 1) NOT NULL, 
     schemaname NVARCHAR(128), 
     tablename  NVARCHAR(128) 
  ); 

INSERT INTO #mdtables 
            (schemaname, 
             tablename) 
VALUES      ('dbo', 
             'user'); 

DECLARE @mdTableLim   INT =0, 
        @mdTableRowId INT =0 

SELECT @mdTableLim = Count(*) 
FROM   #mdtables; 

SET @mdTableRowId = 1; 

WHILE @mdTableRowId <= @mdTableLim 
  BEGIN 
      DECLARE @SDBName   VARCHAR(50) = '[SourceDB]', 
              @TDBName   VARCHAR(50) = '[TargertDB]', 
              @tableName VARCHAR(100) = '' 
      DECLARE @WhereF        VARCHAR(max) ='', 
              @joincondition VARCHAR(max) ='', 
              @or            VARCHAR(10) ='', 
              @select        VARCHAR(max) = '', 
              @comma         VARCHAR(1)='', 
              @query         VARCHAR(max) ='', 
              @and           VARCHAR(5)='', 
              @where1        VARCHAR(1000) ='', 
              @wOR           VARCHAR(5)='' 

      SELECT @tableName = tablename 
      FROM   #mdtables 
      WHERE  id = @mdTableRowId; 

      SELECT @joincondition += Isnull(@and + ( CASE 
                                                 WHEN cu.column_name IS NULL 
                                               THEN 
                                                 NULL 
                                                 ELSE ' src.[' + cu.column_name 
                                                      + 
                                                      '] = ' + 
                                                      'trgt.[' 
                                                      + c.column_name + ']' 
                                               END ), ''), 
             @WhereF += Isnull (@or + ( CASE 
                                          WHEN cu.column_name IS NOT NULL THEN 
                                          NULL 
                                          ELSE Isnull ( '  src.[' + 
                                               TC.column_name 
                                               + 
                                               ']  ', 
                                               ' isnull( src.[' + 
                                               C.column_name + 
                                               '],1)  ' ) 
                                               + Isnull( '<> trgt.[' + 
                                               TC.column_name 
                                               + ']', 
                                               ' = isnull (src.[' 
                                               + 
                                               C.column_name + '],1)  ') 
                                        END ), ''), 
             @or = ( CASE 
                       WHEN cu.column_name IS NOT NULL THEN '' 
                       ELSE ' OR ' 
                     END ), 
             @and = ( CASE 
                        WHEN cu.column_name IS NULL THEN '' 
                        ELSE ' AND ' 
                      END ), 
             @select += @comma + ' src.[' + c.column_name + ']  ' 
                        + Isnull (' , trgt.[' + TC.column_name + ']', ''), 
             @comma = ',', 
             @where1 += Isnull(( @wOR + ( CASE 
                                            WHEN cu.column_name IS NULL THEN 
                                            NULL 
                                            ELSE ' trgt.[' + cu.column_name + 
                                                 '] is null  ' 
                                          END ) ), ''), 
             @wOR = ( CASE 
                        WHEN cu.column_name IS NULL THEN '' 
                        ELSE ' OR ' 
                      END ) 
      FROM   information_schema.columns C 
             LEFT JOIN information_schema.key_column_usage CU 
                    ON C.column_name = cu.column_name 
                       AND constraint_name LIKE 'PK_%' 
                       AND c.table_name = cu.table_name 
             LEFT JOIN [TargertDB].information_schema.columns TC 
                    ON C.column_name = TC.column_name 
                       AND c.table_name = TC.table_name 
      WHERE  c.table_name = @tableName 
             --AND columnproperty(object_id(TABLE_NAME), COLUMN_NAME, 'IsIdentity') = 0    
             AND c.column_name NOT IN ( 'LST_CHG_TMS', 'LST_CHG_TMS', 
                                        'LST_CHG_USR_ID' 
                                        , 
                                        'LST_CHG_USR_ID' ) 
             AND c.data_type NOT IN ( 'image' ) 
      ORDER  BY cu.column_name 

      SET @query = 'select ' + @select + ' from ' + @SDBName + '.dbo.' 
                   + @tableName + ' as src left join  ' + @TDBName 
                   + '.dbo.' + @tableName + ' as trgt on ' 
                   + @joincondition + ' where (' + @where1 + ')' 
                   + Isnull ('and '+ NULLIF (@WhereF, ''), '') 

      DECLARE @qu1 VARCHAR(max) = 
              ' declare @cnt int =0        select @cnt =count (1) from ' 
        + @SDBName + '.dbo.' + @tableName 
        + ' as src left join  ' + @TDBName + '.dbo.' 
        + @tableName + ' as trgt on ' + @joincondition 
        + ' where (' + @where1 + ')' 
        + Isnull (' OR '+ NULLIF (@WhereF, ''), '') 
        + '    if (@cnt>0)       begin     select ''' 
        + @tableName + ''' as [  ],@cnt         ' +-- @query + '    end    ' 

      BEGIN try 
          EXECUTE ( @qu1) 
      END try 

      BEGIN catch 
          PRINT @qu1; 
      END catch 

      SET @mdTableRowId = @mdTableRowId + 1 
  END 

Answer 3

Используйте это как первый оператор выбора:

SELECT  DB1_VIEW.*
   ,CASE WHEN DB2_VIEW.db2_ID IS NOT NULL THEN 'Y' ELSE 'N' END AS Available_db2
,CASE WHEN DB3_VIEW.db3_ID IS NOT NULL THEN 'Y' ELSE 'N' END AS Available_db3

Вы можете удалить все детали, кроме полей идентификаторов в подзапросах db2_view и db3_view.